Is IOWA AGRICULTURAL COLLEGE. [B4 



mollissimus, the outer or } » : 1 1 i - : n I « * layer, is thick and dark, the cells arc elon- 

 gated, like the palisade cells in leaves. They are marked in the upper one 

 third by a light line. The cell cavity is larger at the base, and gradually 

 tapers upwards until it i< quite narrow. The palisade cells show four rather 

 distinct folds, the middle one retracting light strongly; the second layer is 

 composed of thick walled cells; the cavity resembles a dumb-bell in outline. 

 The third layer i^ composed of several rows of thin walled— really differen- 

 tiated- cells, in two parts; the cells of the lower part of the third layer are 

 more irregular than the first. The fourth layer is made up of four row- of 

 cells, which arc elliptical in outline, with a small cell-ca\ ity. The fifth layer 

 is composed of elongated cells similar to those of the fourth. The cells of 

 the sixth layer are very small; some of these occasionally contain an oil 

 globule. The testa of Crotalaria sagittalis is made up of four differentiated 

 layers. The outer is fully one third larger than in Astragalus mollissimus: 

 The light line runs horizontally one fourth the way down from the cuticle. 

 The remaining layers are much like those of Astragalus, excepting the third, 

 Which contains three rows of thin walled cells. The aleurone layer and the 

 starch cell- of the embryo join the inner layer of seed coat-. 





