i6 



PAKT 1. ORGAXOGRAPHV, 



of Crocus and Colchicum are examples. Fig. 24 is a longitudi- 

 nal section of a Crocus corm. At the base is a partially decayed 

 corm of the previous year, and at the apex a large bud. 



The Bulb is an excessively short, erect stem, covered with 

 fleshy scales or leaf-bases, which constitute its principal bulk. 

 A bulb whose leaf-bases form concentric coatings is called a 

 tunicatcd bulb, and one whose scales are imbricated, the outer 



Fig. 25. 



Fig. 26. 



Fig. 27. 



Fig. 25. — Longitudinal section of the Onion, showing the structure of a tunicated bulb. 



Fig. 26. — The scaly bulb of the Lily. 



Fig. 27. — Portion of flattened stem and leaf-like branches of Miihlenbeckia. 



ones not enclosing the inner, is called a scaly bulb. The Onion, 

 Fig. 25 is an example of the former, and the Lily, Fig. 26, of the 

 latter. 



Leaf-Like Stems. 

 Stems occasionally mimic leaves, both in form and function. 

 This is the case with the leaf-like bodies on the stem of the 

 greenhouse Smilax (Myrsiphyllum). Such stems are called 

 cladophylla, and that they are really stems or branches and not 

 leaves is evidenced by the fact that they occur in the axils of 

 scales ; are the product, that is, of axillary buds. Fig. 27 repre- 

 sents a flattened branch of Miihlenbeckia, which performs at 



