Summer Flowers of the High Alps

by Somerville Hastings

Above 6000 feet in the north and 7000 in the south the Conifers become dwarfed and stunted, and gradually disappear to give place to the alpine region. Sometimes as we look along a valley the line of transition is seen to be abrupt and straight, at other times irregular and undulating. Bushes of Alpenrose, Juniper, and Alpine Willow extend upward to the Alpine region, but larger trees are entirely absent. Here are found in profusion the greater number of the plants and flowers peculiar to the Alps. Many of the species may of course be found in sheltered or secluded spots at much lower levels, but here are to be seen in abundance the bright-coloured Saxifrages, Gentians, Anemones, and Pansies, which make the Alps their particular home. Here are the alps or upland pasture grounds of the Swiss, and here are situated the châlets or summer homes of Swiss herdsmen. In June or July, when the pasture is becoming scarce in the valleys and when all the snow is melted on the mountain slopes, the native farmer packs a large copper caldron and whatever else he may require for making cheese into his bullock waggon, and accompanied by his cattle, and often by his family as well, treks upward. The “alps” may be two or three days’ journey from his home, so that he must take with him all that he will probably require for his two or three months’ stay.

The Alpine region extends from the upper tree limit to the snowline, which may be taken as somewhere between 8000 and 9000 feet. Some of the most charming and brightly coloured of Alpine plants like Eritrichium nanum and the Cushion pinks ([Plate 9]) are to be found just below the snowline. Even above this level flowering plants may be met with, for even at the highest altitudes bare rock is to be found from which the snow has been blown by the wind or melted by the sun, or where the slope is too great for more than a very thin covering to remain lodged. The Glacier Crowfoot (Ranunculus glacialis), a pink-flowered buttercup, has for example been found within a short distance of the summit of the Finsteraarhorn, the highest peak in the Bernese Oberland.

Just over two thousand different species of flowering plants are to be found in Switzerland, and a little over half of these are exclusively Alpine. In contrasting the flowers of the Alps with those of our own country, it may be first of all well to consider what we have that Switzerland has not. Of course our seashore plants will be mainly absent, but strange to say a few species of Thrift are here and there found, and the yellow Horned Sea-poppy (Glaucium luteum) even grows in the neighbourhood of Lake Neuchâtel. We are so used to the bluebells of our woods, the purple heather of our heaths, and the yellow gorse of our commons, that we hardly realise how glorious they are. In Switzerland the gorse is very rare, the bluebells are not found at all, and the bell-heathers are absent though the ling is found everywhere. Even the purple foxglove is replaced by a yellow variety. These facts should be borne in mind, lest a too unfavourable comparison be made with our own rich flora.

But the flowers of the mountains are truly wonderful, and it is their abundance as well as their bright colours that make them so striking. At the same time, it must be remembered that though so numerous neither the flowers themselves nor the plants that bear them are really larger than their lowland relatives. Indeed, in spite of their bright conspicuous flowers, the plants that grow at the higher altitudes are generally stunted and dwarfed. Most of the peculiarities of Alpine plants, which we will now enumerate, are to be accounted for by the conditions under which they live. That this is really so is shown by the fact that “within the bounds of what must unquestionably be regarded as a single species, individuals change in character as we ascend to higher altitudes, the leaves become more hairy and more fleshy, and the flowers brighter and larger.” Even more direct evidence of this is to be obtained by cultivating Alpine plants at lower levels and lowland plants at high altitudes. Not a few of the plants of the mountains when grown in our gardens at home change in character very considerably. They tend to elongate so that their leaves are separated by longer intervals of stem, and their hairy characters very largely disappear. The Bearded Bell-flower ([Plate 26]) may lose its bearded character, and the familiar Edelweiss may, in some cases, develop smooth green leaves almost as hairless as those of an ordinary plant. Conversely, we have the observations of Professor Bonnier, who cultivated the plants of the lowlands at high altitudes in the Alps and Pyrenees. Where the plants were able to grow at all they became, in most cases, stunted and dwarfed. The Jerusalem Artichoke, for example, which forms a tall leafy stem like a sunflower in the plains, became a short stumpy plant with leaves arranged in a rosette at its base. Generally speaking, the plants developed a better marked underground stem, and thicker, darker green leaves than the same species grown under more ordinary conditions.

One of the principal characteristics of Alpine plants is the extensive development of the rootstock and underground stem. This is required to protect them against the strong winds, and to extract as large a supply of water and nourishment as possible from the frequently scanty soil. But there is another consideration of at any rate equal importance. During at least half of the year owing to the white coverlet of snow, all activity in the Alpine plant world ceases so that the production of flowers and seeds, indeed all the vital processes of the plants must be crowded into the few months when the ground is clear. Crocuses and Snowbells and other plants are found blooming at the very edge of the snow, therefore everything must be ready for immediate flower production directly the snow melts. For this to take place a reserve store of nourishment is essential, and accordingly Alpine plants are furnished with thick underground stems and fleshy roots where the food substances can be stored.

It is further interesting to note that the number of plants that go through their life cycle in a single year and then die off (annuals as they are called), is in the Alps comparatively small, for most of the plants persist from year to year. Kerner states that while only 44 per cent. of the plants on the Danube plains are perennials, there are as many as 96 per cent. in the Alps. That this has something to do with the conditions under which the plants grow is seen by the fact that the annual meadow-grass (Poa annua) becomes perennial in the Alps. Annuals persist through the winter season, only in the form of seed, so that a single wet summer such as the last (1909), by interfering with the ripening of the seeds, might threaten with extinction an entire species. Annuals have but little food stored up for a sudden outburst of activity on the approach of spring, nor can the tiny root of a budding seedling obtain from the soil all that is necessary for the rapid production of flowers and seeds. Moreover, as we shall see immediately, the production of seeds is in most plants very largely dependent on the presence of insect visitors, and without them either less fertile seeds or no seeds at all are in most cases formed. Insects are said to be less numerous in the Alps than in the plains, and thus the assumption of a perennial character makes the existence of the plant less dependent on external conditions.

Another point which has already been referred to is the low stature and stunted character of so many Alpine plants. Undoubtedly there are marked exceptions, such as the tall Gentians; but, generally speaking, it must be admitted that mountain plants are short stemmed and dwarfed, the vegetative part of the plant being often merely represented by a wreath of leaves. This is also very largely the result of the peculiar conditions of plant-life at high altitudes. The bright sunlight by day and intense cold at night have both a retarding effect on the growth of the stem. As regards light, the converse result is well seen in the long, lanky shoots of a potato growing in a dark cellar. But there is also another factor of some importance. The green leaves of plants are constantly giving out as watery vapour the fluid which has been absorbed by the roots. The decreased atmospheric pressure at high altitudes, the general dryness of the air, and the bright sunlight by day all unite to accelerate this process. During the day the ground is warmed even to a larger extent than the air, and thus the absorption of water by the roots is correspondingly hastened. During the night the intense radiation rapidly cools down the soil on which the plant grows, but the surrounding air is not cooled to anything like the same extent. The result is that the absorption of fluid by the roots is diminished in a much larger degree than the effusion of watery vapour from the leaves, and the plant is in imminent danger of being dried up. To this danger the plants of high altitudes respond in various ways. In the first place, their stunted character not only diminishes the area of leaf surface for the exhalation of watery vapour and protects them to some extent from strong winds, but it also places them in the lowest stratum of air which is most likely to assume the temperature of the soil. The felted, cushion-like habit ([Plate 9]) of so many Alpine plants, and the rosette-like arrangement of their leaves ([Plate 19]), are also of advantage to the plants by exposing less leaf surface directly to the air. The succulent leaves of plants like the house-leeks ([Plates 18 and 19]), and the hairy covering of the Cat’s-foot ([Plate 23]), Edelweiss, and others, seem also designed to counteract the tendency to too rapid desiccation, and the tough leathery character of many leaves ([Plate 7]), and the thickened cuticle of others ([Plate 30]), are clearly of like value. The relatively increased thickness of the leaves of many Alpine plants is also, no doubt, due to the intensity of the sunlight, for direct experiments have shown that increased illumination has this effect. Their usual dark green colour is thought to result from an excess of the green pigment by which plants are able to extract the carbon required for their growth from the air. The rarefaction of the air and shortness of the season of growth at high altitudes, as well as the low stature of most Alpine plants, make it essential that assimilation should take place as rapidly as possible when conditions are favourable for it.

But it is in connection with their flowers that the wonderful adaptation of Alpine plants to their surroundings is perhaps best seen. The plants of high altitudes generally bear more numerous and more brightly coloured flowers than do their relatives of the plains. The low stature of the plants that bear them gives rise to the impression that the flowers of the Alps are also larger than those of lowland districts, but though undoubtedly more numerous and more crowded together they are of about the same size as those of other nearly related species. The colours of the flowers are, however, undoubtedly deeper and more intense. If we examine specimens of the same kind of flower, for instance the Forget-me-not or Eyebright, that have been found growing at different altitudes, we shall be struck with the deeper tints of the flowers from the higher regions. That this character has something to do with the conditions of life in Alpine districts is shown by the disappointment that we sometimes feel at the diminished brilliancy of the flowers of Alpine plants when grown in our gardens at home. The flowers of the Alps are also, as a rule, of a more highly organised type than those of the plains, and corresponding with this increase in complexity is a relative increase in the number of pink and blue flowers, and a diminution in that of the yellow and white. Alpine plants, too, seem to produce more honey than do the corresponding plants in the plains; at any rate, the yield of honey from bee-hives is greater, and Bonnier has shown that the secretion of honey by flowers of the same kind increases with the altitude, and that in some cases there is a corresponding increase in the intensity of the scent of the flower.

While many of the characteristics of Alpine flowers are to be explained as a direct result of the conditions of life at high altitudes, it is probable that the process of natural selection has also had a good deal to do with their production. One of the principal objects of the life of a flowering plant is to produce seeds. It has been shown that, generally speaking, more numerous and healthier seeds are produced when the seed-producing apparatus of a flower is fertilised by pollen from the stamens of a flower of a different plant. Hence arrangements have to be made by plants for the conveyance of their pollen from flower to flower. This is sometimes effected by the wind, but much pollen is lost, so that this is manifestly a very wasteful method. Plants have therefore adopted the more economical plan of getting insect visitors to do this carrying business for them. The bright colours and sweet scents are to attract insects to the flower, and honey is provided for their entertainment there. It is generally believed that the total number of insect visitors in the Alps is less than in the plains, and therefore the competition for their services being more severe, greater attractions in the form of brighter coloured flowers and more abundant honey have to be provided for them. But, unfortunately, the direct observations of H. Müller do not confirm this view. There can be no question, however, that the relative proportion of the several varieties of insects in the Alps is very different from that in the plains. There are comparatively few flies, bees, and wasps, but numerous humble-bees, butterflies, and moths in the mountain regions. These insects have longer tongues and prefer to visit flowers of a more complicated structure, where the honey cannot be reached by their shorter tongued relatives. Flowers of this sort with less easily obtained honey are more often of a red or blue or pink colour, and more rarely of a yellow tint. Not a few Alpine flowers like the Aconites ([Plates 3 and 4]) are entirely dependent on humble-bees for their fertilisation, and an even larger number, such as the Long-Spurred Pansy ([Plate 5]), and several of the Gentians are exclusively visited by butterflies and moths. Müller even goes so far as to suggest that not a few of the Alpine flowers, especially those of a pale crimson colour and with a clove-like smell, such as the Pinks ([Plate 9]), have been evolved in the Alps under the influence of butterflies and moths. In spite of this it is curious to note that the number of flowers that are habitually self-fertilised is greater in the Alps than in the plains. But when it is explained that these are for the most part of the same type of flower that is pollinated by flies, bees, and wasps in lowland districts the apparent anomaly becomes clear.