THE STEM AMJ ITS FUNCTIONS 95 



Beneath this is the cortex, varying in thickness ])ut rare!}' oceupy- 

 ing as prominent a place in the stem as it does in the root. 

 Beneath the cortex hes the jibro-vascular cylinder which, iinhke 

 its counterpart in the root, is arranged in the form of a hollow 

 tube. The core of this tube is occupied by the yith, a tissue 



Fig. 47. — Bulb and corm. {A), longitudinal section through the bulb of a 

 hyacinth. The short, broad stem bears a cluster of fleshy leaves, the central ones 

 of which grow out as foliage leaves. {B) , longitudinal section through the corm of 

 a crocus, showing the thick, short stem surrounded by the fibrous remains of old 

 leaf-bases. The remains of corms of three preceding seasons are shown below 

 the present one. The tops of the leaves have been cut off in both illustrations. 



much resembling the cortex. A more detailed account of the 

 character of the cells composing these tissues may be appropri- 

 ately undertaken now, for although all the tissues here men- 

 tioned are present in root, stem, and leaf, they reach their greatest 

 differentiation and complexity in the stem, and in this region of 

 the plant they can therefore most profitably be studied. The 

 structure of the fibro-vaseular tissues of a wood}- dicotyledonous 

 plant can well be seen in Figs. 49 "and 50, a transverse and a radial 

 longitudinal section through a portion of the stem shown in 

 Fig. 48. 



