296 KANSAS UNIVERSITY SCIENCE BULLETIN. 



The bundles at the corners show a diminution of both sieve 

 tubes and water tubes, the associated bast and wood fibers 

 being especially developed. (See fig. 6.) 



The pith (fig. 1, is very prominent. The large cells in the 

 central portion with unlignified walls (fig. 2, w) are in con- 

 trast to the smaller cells near the bundles with walls lignified. 

 A peculiar arrangement is to be noticed at the corners (fig. 6). 

 Just inside the xylem is a region of unlignified cells (fig. 6, v) , 

 resembling an inner phloem, and surrounded, toward the pith, 

 by a region of lignified pith cells (fig. 6, p). The pith contains 

 numerous air spaces (fig. 2, g), but no extensive cavities of 

 any kind. 



THE LEAF. 



The leaves of alfalfa are pinnately compound, each petiole 

 bearing three leaflets, the characteristic leaf-type of clover. 

 Each leaflet has a small petiolule, is elliptical in general out- 

 line, much more narrow than long, and with prominent teeth 

 on the margins towards the tips (fig. 41, s) . It is very notice- 

 able that these teeth are the terminating points for the main 

 branches of the system of veins (fig. 41). These terminations 

 may be of the nature of hydatodes, as they seemed in some 

 plants to act as drip tips. Beads of water were observed to 

 accumulate at these tips after the plant was covered with a 

 bell jar over night. 



At the base of the petiole are attached two stipules, which 

 are leaf-like in structure, and probably do some of the ordi- 

 nary work of leaves. In cross section (fig. 24) the petiole ap- 

 pears heart-shaped, and the three vascular bundles (fig. 24, z), 

 which extend into the three leaflets to form their midribs, are 

 arranged in an arc. This arrangement is quite characteristic 

 in the Papilionacese with three leaflets. No medullary rays 

 are found in the petioles of any of the Papilionacese. Each 

 leaflet petiole (fig. 25) is much like the leaf petiole, except that 

 in section only one vascular bundle appears (fig. 35). The 

 cells next the epidermis are full of stored food material, mostly 

 starch. 



The epidermis of the leaf is made up of irregularly shaped 

 cells (fig. 14), the outer walls of which are strongly cutinized 

 (fig. 17). There are numerous trichomes on both surfaces of 

 the leaf, as well as stomata, both being slightly more numerous 

 on the under surface. 



