94 



ILLINOIS STATE ACADEMY OF SCIENCE 



of two wax models ; one of the region of the cotyledonary 

 plate, the other the region of the epicotyl. This seed- 

 ling has a short, thick, evanescent primary root, which 

 never emerges from the surrounding embryonal tissues. 

 Primary roots have four protoxylem strands. Each half 

 of each strand separates from its fellow and these eight 

 strands form a ring at the base of the cotyledonary 

 plate, the phloem being placed outside of the xylem. As 



Fig. 13. 



the embryo grows, one broad bundle from each side of 

 the ring is laid down in each cotyledon. Each of these 

 proves to be a complex of a number of bundles, twelve 

 in this seedling, which can be separated into three groups, 

 the various bundles meeting and parting again, thus 

 forming the lattice work vascular structure of the typical 

 monocotyledon, a polystelic vascular system (Fig. 12). 



