91 



Finally, there are species whose individual evolution is very slow, and in which the vegetative 

 organs of the young plant, especially its leaves, have a juvenile aspect so pronounced that they entirely 

 differ from those of the adult plant. This may, moreover, manifest itself in two ways. Generally the 

 most developed leaves of the young plant, those that I shall call henceforth the juvenile leaves, are in 

 shape and internal structure simpler than the leaves arising later on the adult plant. But there are also 

 species in which it is, on the contrary, the adult plant which presents the least complicated vegetative 

 organs, as one sees, for example, in the phyllodes of Acacia. Therefore,- in either case, the adventitious 

 shoots of the adult plant are always in the beginning leaves of the juvenile form-.- 



This general characteristic of adventitious shoots has been for a long time unrecognised. Schacht 

 seems to me the first who has mentioned it. One finds in his Traite* a short passage'in which bespeaks 

 of it apropos of the Canary Island Pine. However, many other trees, and some of the most common in 

 Europe, furnish still more striking examples of this phenomenon. Also it is singular that there is no 

 question either in the Morpliologie of Hofrneister, nor even in the Memoir of Alexander Braun on the 

 Individu Vegetal. This characteristic trait of the adventitious shoots is similarly entirely passed over in 

 silence in modern treatises. Yet, moreover, an eminent Italian botanist, the late G. A. Pasquale, had 

 long ago specially called the attention of niorphologists to it. This is how he expresses himself on the 

 subject in his memoir on heterophylly (Sulla Eterophylla, p. 22), which appeared at Naples in 1867 : — 



" In the course of all these generations of buds and shoots which succeed each other indefinitely 

 on the arborescent plant, one would not again see the forms of the youthful stage, if it did not reproduce 

 in indeterminate points of the axis another sort of bud, which strongly resemble the young plant, and 

 which produce its form and even its colour. These are the adventitious buds which in Pines show them- 

 selves freely on the trunk and even on the branches. These adventitious buds enclose the new shoot, 

 which repeats the primitive form of the young plant in everything that it has produced above its cotyledons. 

 It is seen, therefore, that every time one finds juvenile branches with their special leaves on an adult tree 

 or a large one, or even an old one, that this is the result of the accidental formation of adventitious buds. 

 And this phenomenon, the cause of which resides in the plant, can also be produced at will by methods 

 which tend to cause the formation of adventitious buds similar in shape and all other characters belonging 

 to the free development of the trunk and branches. So that, if one wishes to see the juvenile forms 

 reproduce themselves on a tree, one has only to cause adventitious buds to shoot. Similar cases to those 

 I have quoted are seen in Schinus, Eucalyptus, Pinus, &c." 



Further on the author adds this remark, to which I shall have to return : — " In the very small 

 adventitious buds of JZsculus Hippocastanum are found leaves with three leaflets ; that is to say, of simpler 

 form than in the plantlet resulting from germination." 



The quotations from the memoir of Pasquale show with what perspicacity and neatness of expression 

 this scholar had recognised and shown the special nature of adventitious buds, and the exact position 

 that they occupied in the ontogenic development of the plant. This memoir is not less remarkable and 

 instructive, because of the rational method with which he treats of what has been improperly called 

 Vegetable Metamorphosis. When, fixing on the study of the internal study of leaves, I myself studied 

 later this supposed metamorphosis as a fact of heterophylly, due to the unequal development of the 

 phyllomes, 1 I was then ignorant that this same idea was already expressed in the memoir of Pasquale. 

 The correctness of this point of view is to-day proved, thanks to the observations and experience of Herr 

 Goebel. Indeed, by an ingenious application of the pruning, not only of the vegetative axes, but also 

 of their appendicular organs, he has succeeded in causing an increase of development in the phyllomes, 

 which, according to their position on the plant, should have maintained the rudimentary state of the bud 

 scales and caused them to assume the forms of true leaves. 2 



To return to the memoir of Pasquale, it is indeed a pity that this masterly work has not received 

 the attention of contemporary botanists. One might almost say that it has been passed almost unnoticed, 

 for the too brief review of it in the Bull, de la Soc. Bolanique de France 3 does not truly give an idea of 

 its real value. 



* Handbuch v. 2 p. 11. This is the translation of the passage in question : — "While our fir-trees never produce 

 adventitious buds, many of those in America are remarkable for the facility with which they produce them. And even 

 in the case of the beautiful Canary Island Pine [Abies Canariensis), when the branches have been removed; the trunk is 

 covered with young shoots which have, like the young plants of the ordinar}' firs, long leaves, in the axils of which there 

 grow later three needles in one sheath. 



1 Mem. Soc. Phys. et Hist. nat. Gen. t. xxvi, 2, 1879, p. 453. Vol. Cent. 1890, p. 30. 



2 " Beitrage zur Morphologie und Physioldes Blattes." Botan. Zeit, 1880, p. 803. 

 » Tome xiv, 1867, p. 153. 



