292 KANSAS UNIVERSITY SCIENCE BULLETIN. 



below the surface, giving rise to a group of heavy, downward- 

 directed secondary roots. Such a root system affords an ex- 

 tensive connection with the soil reservoir, and partly accounts 

 for the ability of a stand to produce three to five crops in a 

 summer. In this extensive root system also, a considerable 

 amount of food storage over winter is made possible. The 

 upper portions of the roots vvere found to be packed with food 

 in the fall. In the spring this food was used in the new growth. 

 During the winter a pronounced concentration of food at the 

 bases of the buds was noticeable. Although in no way excep- 

 tional structurally, the anatomy of the root may be briefly con- 

 sidered. 



A cross section of the young root (fig. 1) shows a protostele 

 of the primitive exarch type. A protoxylem point is shown at 

 (c) . In the later stage a circle of collateral vascular bundles is 

 apparent, with pith rays radiating from the original proto- 

 xylem points. At this stage the root is much like the stem in 

 general appearance of the cross section. Just outside the 

 phloem is a cylinder of pericycle surrounded by larger cells 

 (d) with more or less lignified walls. This cylinder lends 

 strength to the root and protection to the tender phloem region. 

 Such a protective tissue is especially serviceable, since the 

 outer or cortical region (c) of the bark soon breaks down as 

 shown. 



THE STEM. 



Alfalfa is a perennial herb, giving rise each spring to a 

 crown of stems from a persistent root system. This crown 

 arrangement of stems accounts for the luxuriant cover of 

 growth in an alfalfa field, when the single plants may be a foot 

 or more apart. 



A cross section of a stem of alfalfa appears as shown in fig- 

 ure 2. The epidermis is multiple, being made up of two layers, 

 quite similar in cell structure. (Fig. 2, /.) The outer layer of 

 cells has a more thickened and cutinized outer wall. The cor- 

 ners of the somewhat four-angled stem show a multiplication 

 of the cell layers under the epidermis, seemingly serving for 

 greater strength. (Fig. 2, g.) Between the epidermal region 

 and the groups of bast fibers (fig. 2, li) is an extensive tissue 

 (fig. 2, /), which bears numerous chloroplasts in the cells. 

 The chloroplasts are not shown in the figure. The groups of 

 bast fibers (fig. 2, h) are just outside the phloem region 



