268 MORPHOLOGY. 



I must here particularly remark, that there is no sense in explaining 

 the triangular leaves, e. g. in some species of Mesembryanthemum, as 

 leaves originally plane, which were then folded back and grew toge- 

 ther by the posterior surface, or in regarding the leaf of the Iris as one 

 folded together on the upper face, and with the sides grown together. 

 The only proof which could be given of this would be the history of de- 

 velopment, and this shows that such folds and growings together do not 

 occur, but that, formed originally like all other leaves, the latter leaf ex- 

 pands into a vertical plate, the former into a triangular one, and nothing 

 more. Through nothing else whatever can natural laws be established, 

 but we must trace back all forms to one, or rather deduce all from one. 

 That assertion would have a meaning only under the presupposition of 

 such a natural law. But the mere fiction of such a natural law may be 

 unconditionally repulsed. According to a fiction of Link's, in the same 

 way arbitrarily manufactured, the leaves of Abies excelsa, alba, &c. ori- 

 ginate from two with the upper faces grown together, which one sees 

 in the two mid-nerves projecting above and below. Truly Abies pecti- 

 nata and Pinus sylvestris have an indication of two free, parallel, vascular 

 bundles, but Abies excelsa, alba, &c. only of one, and in the latter the 

 upper and under halves are of a totally different structure ; finally, the 

 history of development shows decisively that only one leaf exists here, 

 and not two grown together. 



I will add a few words respecting the pouches or pitchers which occur 

 in Nepenthes, Sarracenia, Cephalotus, Dischidia Rafflesiana and cla- 

 vata, Marcgravia, Norantea, Utricularia, &c. At present we have not 

 a complete history of development of a single species. The researches 

 which I made formerly into Utricularia unfortunately still remain very 

 imperfect. The pouches apparently present three different types : a. 

 In Sarracenia it is the lower part of the leaf which exhibits a form resem- 

 bling a cornucopia, while at the upper border runs out a flat expansion 

 (the lamina of the leaf) separated from the pouch by a deep incision on 

 each side. The lower half of the internal surface of the pouch is clothed 

 with hairs, directed downwards ; the upper part is smooth. In Nepen- 

 thes a pitcher-shaped structure is borne upon a long petiole, winged 

 below, then often tendril-like, and carries upon its upper border an 

 articulated (?) lamina, which originally closes the pitcher like a lid. The 

 inner surface is clothed in the lower part with little papillae of very de- 

 licate, succulent cellular tissue, while above the epidermis projects down 

 over these like the eaves of a house. In both, the cavity is formed from 

 the leaf in such a manner that the closed base of the pouch corresponds 

 to the base of the leaf (Sarracenia), or lies quite close to it (Nepenthes). 

 In Dischidia Rafflesiana and clavata, on the contrary, the opening of the 

 pouch is turned towards the base of the leaf; Cephalotus appears to 

 possess a structure similar to that of Sarracenia* In all the plants men- 

 tioned the pouch constitutes the main body of the leaf. (Some have 

 found pleasure in debating whether the lid in Sarracenia and Nepenthes 

 is the blade of the leaf or not, and how the individual parts are to be 

 traced back to the supposed normal leaf.) b. In Marcgravia and No- 

 rantea, on the other hand, according to Lindley, the pouches are formed 

 by the stipules, c. Lastly, in Utricularia, many separate little portions 

 of the greatly divided leaf unite to assume a very complicated form of 

 pouch. Originally these form a little, shortly-stalked, somewhat cornet- 



* I only know Cephalotus and Dischidia from descriptions. 



