292 LEAVES OF CERATOPHYLLUM. [BOOK i. 



The form of the leaves composing the first distinct whorls, 

 is that of a rounded and nearly plane crenel. One of the 

 whorls, if isolated, looks like a ring deeply crenate on its 

 upper edge ; each crenel corresponds with a bifurcation of the 

 perfect leaf. All these crenels are originally equal in size, 

 and joined together in pairs, or in fours at their base : the 

 incisions never penetrate as far as the base of the leaves. 



The succeeding transformations are caused by the crenels 

 becoming a little pointed and unequal, at the same time that 

 the incisions penetrate further into the common base, whence 

 results a four-cleft palmate scale, the lobes of which are of un- 

 equal length. This form is already tolerably like that of the 

 completely developed leaf. After a time the scale grows princi- 

 pally in length : the four points are more distinctly separated, 

 the middle ones always remain the longest, their edges become 

 covered with peculiar tumours, their summit is crowned with 

 a cellular appendage, and lastly the leaf, originally quadri- 

 crenate, becomes dichotomous. 



The cellular appendage found at the top of each fork merits 

 some detail. From the time that each point of the fork is a 

 rounded crenel, the extremity is found to be composed of 

 five, six, or more, very small transparent cells, whilst the rest 

 of the mass is opaque, yellowish, and without distinct cellular 

 sides. In proportion as the crenels grow larger, the cellules 

 at the top also become larger, and several other similar cells 

 are added to them - 3 they are all placed on the immediate limit 

 of the edge. These cellules afterwards distinctly project 

 beyond the edge ; the terminal ones increase in number, 

 and form a string of three or four series, terminated by one 

 solitary cellule, and lying on a base of several more transpa- 

 rent cellules. This thread acquires its greatest vigour on 

 leaves that are almost completely formed ; it then becomes 

 attenuated into a brownish thread, and disappears altogether 

 when the leaf is in its last stage of development. The cellules 

 of this string are oblong oval, translucent, and filled with 

 whitish, transparent, irregularly shaped corpuscles, which 

 appear to be grains of starch, but may possibly be cytoblasts 

 beginning to be dissolved. This string, looking at the way in 

 which it is formed, and its short duration, may be compared 



