As an example of the extent to which unessential differences may go, he says (p. xvii.,) “The few remaining native Cedars of Lebanon may be abnormal states of the tree which was once spread over the whole of the Lebanon; for there are now growing in England varieties of it which have no existence in a wild state. Some of them closely resemble the Cedars of Atlas and of the Himalayas (Deodar;) and the absence of any valid botanical differences tends to prove that all, though generally supposed to be different species, are one.”
Still the great majority of the species of plants in those Southern regions are peculiar. “There are upwards of 100 genera, subgenera, or other well marked groups of plants, entirely or nearly confined to New Zealand, Australia, and extra-tropical South America. They are represented by one or more species in two or more of those countries, and thus effect a botanical relationship or affinity between them all which every botanist appreciates.”
In reference to the History of Botany, I have received corrections and remarks from Dr. Hooker, with which I am allowed to enrich my pages.
“P. 359. [Note 3]. Nelumbium speciosum, the Lotus of India. The Nelumbium does not float, but raises both leaf and flower several feet above the water: the Nymphæa Lotus has floating leaves. Both enter largely into the symbolism of the Hindoos, and are often confounded. [633]
“P. 362. [Note 5]. For Arachnis read Arachis. The Arachidna of Theophrastus cannot, however, be the Arachis or ground-nut.
“Pp. [388] and [394]. For Harlecamp read Hartecamp.
“P. [394]. For Kerlen read Kalm.
“P. [394]. For Asbech read Osbeck.
“P. [386]. John Ray. Ray was further the author of the present Natural System in its most comprehensive sense. He first divided plants into Flowerless and Flowering; and the latter into Monocotyledonous and Dicotyledonous:—’Floriferas dividemus in Dicotyledones, quarum semina sata binis foliis, seminalibus dictis, quæ cotyledonorum usum præstant, e terra exeunt, vel in binos saltem lobos dividuntur, quamvis eos supra terram foliorum specie non efferant; et Monocotyledones, quæ nec folia bina seminalia efferunt nec lobos binos condunt. Hæc divisio ad arbores etiam extendi potest; siquidem Palmæ et congeneres hoc respectu eodem modo a reliquis arboribus differunt quo Monocotyledones a reliquis herbis.’
“P. [408]. Endogenous and Exogenous Growth. The exact course of the wood fibres which traverse the stems of both Monocotyledonous and Dicotyledonous plants has been only lately discovered. In the Monocotyledons, those fibres are collected in bundles, which follow a very peculiar course:—from the base of each leaf they may be followed downwards and inwards, towards the axis of the trunk, when they form an arch with the convexity to the centre; and curving outwards again reach the circumference, where they are lost amongst the previously deposited fibres. The intrusion of the bases of these bundles amongst those already deposited, causes the circumference of the stem to be harder than the centre; and as all these arcs have a short course (their chords being nearly equal), the trunk does not increase in girth, and grows at the apex only. The wood-bundles are here definite. In the Dicotyledonous trunks, the layers of wood run in parallel courses from the base to the top of the trunk, each externally to that last formed, and the trunk increases both in height and girth; the wood-bundles are here indefinite.