CHAPTER XXVI.
The Life of a Fern.1
1 For this chapter I am indebted to my friend Mr. William Whitwell, of Oxford.
One of the most marvellous of "the fairy tales of science" has now to engage our attention for a time. The growth and fertilization of the seeds—more properly called spores—of ferns, present phenomena of remarkable singularity and interest. Growth is advisedly named first, as in the present instance it really does occur before fertilization, which is not the primary event in the life-history of a fern.
But a few words must be devoted to the preliminary question: What is a fern?
The vegetable kingdom is divided into two great provinces, allotted respectively to the flowering and the flowerless tribes. The flowering plants have several distinct and visible organs for the formation and fertilization of their seed, to each of which is assigned a special and necessary office. In the flowerless section, on the contrary, there are none of these visibly separate agencies in reproduction, and what are usually termed the seeds do not show any parts representative of the developed product. In the true seeds, which belong to flowering plants alone, are contained the rudiments of a stem, leaves, and root, but in the spores of the flowerless plants nothing of the kind is found. The spores, again, are microscopic, while the smallest of true seeds can be not only seen but easily picked up. You have, doubtless, met with the peculiar fungus called a puff-ball, and amused yourselves by watching the little clouds of impalpable dust which are shaken from it on the slightest motion. Those fine clouds, not nearly so visible as a film of candle smoke, are composed of innumerable spores, and such are the representatives of seeds in every member of the great section of the flowerless plants.
Now it is peculiar to ferns, that the cases in which these spores are enclosed grow directly from the veins of what is usually called the leaf, but is more correctly termed the frond, and always appear upon the back or at the margin.
Ferns, then, are flowerless plants which bear their spores in cases growing upon the back or margin of the leaves.
In order that the phenomena of growth and fertilization in ferns may be clearly understood, it is necessary to refer to the process as taking place in flowering plants. The tulip is most appropriate for an illustration, inasmuch as its various parts will be recognised with ease.