276 Sc hivcly— Contributions to the Life History of 



general coloration, that seen in the terrestrial, but the 

 depth of the layer is nearly twice as great as that in the ter- 

 restrial (Plate XX., Fig. 9, a). Beneath is a row of curiously 

 shaped cells, that are strongly thickened and possess flanges 

 abutting upon each other. Six or eight rows of cells lie 

 below this, showing a gradual or sudden change from indu- 

 rated to parenchymatous type, according to the region of 

 the seed from which the section is taken. In the region of 

 the hilum all of the above layers increase remarkably in 

 size and thickness. Forming the chalaza are numerous 

 pitted and reticulate tracheids, of the character usually 

 found toward the termination of vascular areas. In this 

 part of the seed, lying between the tegmen and the cotyle- 

 dons, is a narrow tapering band of sclerenchyma, limited 

 in extent. Bordering directly upon the cotyledons is the 

 inner epidermis of the coat ; this consists of narrow elongated 

 cells. Immediately above these epidermal cells are two, 

 occasionally three, layers of strongly indurated elements 



(Fig. 9 b). 



The seeds of the three aerial types, like those of the ter- 

 restrial, are exalbuminous. In the aerial seeds the prevail- 

 ing shape of the starch granules is spherical ; they are 

 smaller than those of the terrestrial. The proportion of 

 proteid seems greater in the former than in the latter. 



Weight. 



Equal numbers of terrestrial and of aerial seeds were 

 weighed, and then dried in the oven for from two to four 

 hours at a temperature of about 8o° C. The results have 

 been arranged so that comparisons of the weights of a 

 single seed of each class may be made. 



Small terrestrial seeds weighed about .345 grammes; 

 after drying, .181 grammes. Medium sized seeds weighed 

 1. 143 grammes ; after drying, .605 grammes. In a certain 

 locality near Burmont, several exceedingly large specimens 

 were found. The weight of one of these was 2.601 grammes ; 

 after drying, 1.1711 grammes. Thus it will be seen how 



