210 The AMERICAN MONTHLY [July 



addition of water, the cell walls become mucilaginous, 

 elongate, stratification becomes evident, the cuticle 

 breaks and an irregular surface is formed. The second 

 layer is but slightly developed, made up of thin walled 

 parenchyma cells. The cells of third layer are elongated 

 and thickened laterally. These cells are much longer 

 than in B. nigra and brown in color. The fourth layer 

 consists of one to two rows of rather thin walled cells 

 carrying pigment. Endosperm consists of several rows 

 of cells ; first row nearly isodiametric, filled with pro- 

 tein grains. The three or four layers of cells following 

 are thick walled with a small cell -cavity. 



Embryo. — First layer of cells nearly isodiametric, 

 those following somewhat larger, filled with protein and 



fat grains. 



Brassica alba, Boiss. 



Pod very bristly, spreading. Seeds pale yellow, round 

 or somewhat oblong, one to one and a half lines in 

 diameter, average a little over a line. Cotyledons incum- 

 bent, folded around the caulicle. 



The seeds of this species have been studied by many 

 investigators. Parts of the seed are much stronger 

 developed than in B. nigra. The first layer of cells is 

 covered by the well developed cuticle. On the addition 

 of water a copious mucilage is developed, the cell wall 

 becomes strongly stratified. A portion of cell wall sur- 

 rounding the cell cavity is more yellow and has a strati- 

 fication of its own. When water has been allowed to act 

 for some time, the cuticle breaks, thus causing an irregu- 

 lar margin. Cells of the second layer are somewhat 

 irregular, thin walled, with a large cell cavity and small 

 intercellular spaces ; as a rule composed of a single 

 layer of cells but in some places two well developed 

 layers! The third layer consists of cells with lateral 

 thickened walls, which contain a yellow pigment. Cells 

 in the fourth layer are also thick walled. 

 (To be Continued.) 



