PHANEROGAMIA : FOLIAE ORGANS. 261 



c. With underground stems, stalks above ground, undershrub 



(suffrutex\ e. g., Aconitum Napellus, P&onia officinalis : 



d. Stem branched from below, without predominance of the main 



stem, bush (frutex), e. g., Prunus spinosa, Juniperus Sabina : 



e. Trunk, the lower branches of which soon die, and which only 



bears a crown, tree (arbor), e. g., Pyrus torminalis, Fagus 



sylvatica. 



N. B. We also reckon among trees those stems also which 

 branch from below upward, but in which the main axis is 

 developed in far the greatest proportion, and may readily be 

 traced to the summit, e. g., Populus dilatata, Abies excelsa. 

 These might even be called ar bores fruticosce. 



C. FOLIAR ORGANS. 

 a. Foliar Organs in general. 



131. The leaves (JoKa) also may be divided into annual (folia 

 annua) and perennial (f. perennid) ; the former again into deci- 

 duous (f. decidua), which live only in the early part of the period 

 of vegetation ; yearling leaves (f. annua sensu stricto), which live 

 through the whole period ; and late leaves (/. serotina), which are 

 not perfected till toward the close of the period. With few ex- 

 ceptions every plant has temporary leaves, namely, the cotyledons 

 and frequently those next following them. The Orchidacece, some 

 species of Cuscuta *, and some Cactacece, are the only plants at pre- 

 sent known with certainty to be destitute of cotyledons. Others, 

 for instance the Rhizanthece, have not yet been sufficiently inves- 

 tigated. Many plants are wholly destitute of foliar organs between 

 the cotyledons and the peduncles of the flowers, as, for instance, all 

 the Cactacece, excepting Peireskia, and some species of Opuntia ; 

 in others these are annual, as in Alnus, or perennial, as in Pinus. 

 The floral parts, the leaves last perfected, exist in all Phanero- 

 gamous plants. 



I. The general character of all foliar organs lies solely in the 

 history of development, as already has been shown ( 120.). It 

 follows from what was said there, that the leaf is, as it were, pushed 

 out from the axis; that the summit is its oldest, the base its 

 youngest part. It follows, moreover, that the power of develop- 

 ment in a leaf is limited, and never persists long when the terminal 

 shoot becomes removed from it by onward growth. Finally, 

 observation of the course of development also shows that the foliar 

 organ is altogether determined by the axis, as a definite product of 

 the fashioning organisation, that a protracted duration of the pro- 

 cess of development may indeed somewhat increase the volume 



* In Cuscuta monogyna, for instance, the embryo has distinct foliar organs. 

 C. americana, arvensis, congesta, epilinum, epithymum, europcca, nitida, umbrosa, have no 

 trace of them. 



s 3 



