A HISTORY OF SCIENCE 



ing leaves of the stalk stand alternately upon it. Here 

 we see an approximation and a joining of parts which 

 nature afterwards separates and places at a distance 

 from one another. It is still more remarkable when 

 the cotyledons take the form of many little leaves 

 gathered about an axis, and the stalk which grows 

 gradually from their midst produces the following 

 leaves arranged around it singly in a whorl. This may 

 be observed very exactly in the growth of the pinus 

 species. Here a corolla of needles forms at the same 

 time a calyx, and we shall have occasion to remember 

 the present case in connection with similar phenomena 

 later. 



" On the other hand, we observe that even the coty- 

 ledons which are most like a leaf when compared with 

 the following leaves of the stalk are always more un- 

 developed or less developed. This is chiefly noticeable 

 in their margin which is extremely simple and shows 

 few traces of indentation. 



" A few or many of the next following leaves are often 

 already present in the seed, and lie enclosed between 

 the cotyledons; in their folded state they are known 

 by the name of plumules. Their form, as compared 

 with the cotyledons and the following leaves, varies in 

 different plants. Their chief point of variance, how- 

 ever, from the cotyledons is that they are flat, deli- 

 cate, and formed like real leaves generally. They are 

 wholly green, rest on a visible node, and can no longer 

 deny their relationship to the following leaves of the 

 stalk, to which, however, they are usually still inferior, 

 in so far as that their margin is not completely devel- 

 oped. 



142 



