202 Trails. Acad. Sci. of St. Louis. 



grains. The component parts are angular. The grains are 

 without an organic center. The large compound starch grains 

 are not evident except when carefully treated, especially not 

 in products that are manufactured from it, as rice flour. 

 Acording to Harz 1 the structure of Leersia oryzoides is 

 similar to that of Oryza (PI. XVII. 4). 



Zizania aquaiica, L. The pericarp as well as the testa is 

 colored brown, in some cases almost black. They are, how- 

 ever, but slightly developed. The pericarp consists of a single 

 row or at most two rows of cells. These are not much longer 

 than broad and rather thick-walled. The paricarp is followed 

 by several rows of larger cells but somewhat thinner walled. 

 The walls of the testa are thicker, the cells are smaller, they 

 are likewise colored brown. In the mature specimens there is 

 no evidence of remnants of the nucellus except in a few places 

 where it is strongly compressed. The aleurone layer consists 

 of a single row of somewhat tabular cells. The vitreous starch 

 layer contains large compound and some simple grains (PI. 

 XVII. 1). 



MAYDEAE. 



Two genera were studied, Euchlaena and Zea. 



Zea Mays, L. I have in another connection discussed the 

 structure of Zea. 2 The pericarp consists of thick-walled 

 epidermal cells followed by a layer of variable thicknesses, the 

 walls of which are greatly thickened, with radiating pore canals. 

 The testa is insignificant, the walls are thinner than in pericarp. 

 Remnants of the nucellus may be distinguished in some parts 

 of the seed. This is followed by the endosperm. The aleur- 

 one cells are smaller, very different from those underlying it. 

 The starch cells following the aleurone are closely packed 

 and filled with angular starch grains (PL XIX. 11). 



Euchlaena mexicana, Schrad. Teosinte is closely related to 

 Zea. 3 Its structure is very different from that of Zea.* The 



i I.e. 1280. /. 171, IV-VI. 



2 Comparative anatomy of the corn caryopsis. Proc. la. Acad. Sci. 5: 

 199-203. /. 5-10. 1897.— Contr. Bot. Dep. la. State Coll. Agr. & Mechanic 

 Arts. 10. 



3 Harshberger, Garden & Forest 9: 522, considers our corn to have been 

 derived from Zea canina Watson and Euchlaena mexicana. 



i Harz, 1. c. 1249, has given a brief account of its structure. 



