The Microscope. I'Jo 



hull it appears to be composed of three layers, but by softening the 

 hull with potash and isolating its elements it is found to be 

 composed of two layers of very different cells. The outer layer of 

 the hull consists of densely packed columnar cells, irresistibly 

 reminding one of the basaltic structure of the famous Giants' Cause- 

 way. These cells are disposed with their long axis radial to the 

 meat and are of a different consistency at the two ends, so that 

 when a radial section of the hull is viewed it is traversed by a dark 

 line parallel with the outer surface and about one-third of the width 

 of the section therefrom, giving the appearance of two layers of 

 columnar cells, which is, however, shown to be illusory by the fact 

 that the cells may be very readily separated from each other, and 

 the isolated cells show the appearance noted to be due simply to 

 difference in structure in the two parts of the cell. 



Fig. 3, Section of Hull. 3a, Cells separated. 



The inner layer of the hull, which separates readily from the 

 outer layer, is composed of compressed cells, which, when softened, 

 swell up into rudely cubical cells, three or four tiers of which com- 

 pose the inner layer, and, being hard and woody, form a smooth 

 inner surface to the shell. 



Fig. 3b, Inner cells separated. 



The cells of the outer layer are from .18 to .25 Mm. long by 

 .03 Mm. in diameter; those of the inner layer are about .OG Mm. in 

 the longer dimension. 



The kernel of the seed, known in the trade as "meats," is 

 composed of the intimately plicate cotyledons of the seed, enclosing 

 the radicle, the whole enclosed in a membrane investing the kernel 

 and forming a considerable part of the meal of the seed. This 

 investing membrane is composed of two layers of small compressed 

 cells, and is lined with an extremely thin membranous lining, which 

 can be separated after boiling in acid, and then displays no distinct 

 structure. The kernel proper, formed by the cotyledons and radi- 

 cel, consists of compacted cells, intei'spersed among which are a 

 multitude of minute, globular oleo-resin cells, or glands, commonly 

 called "oil-cells," having a diameter of about .10 Mm., but variable 

 in size. 



Fig. 4. Section of Kernel. 4a, Oil-cells. 



The cellular structure of the cotyledons consists of a super- 

 ficial layer of cells regularly disposed in two tiers, with the paren- 

 chymal cells and oleo-resin glands filling the interspace. The 



