SEEDS. HI 



In order, however, to utilise these differences to the fullest pos- 

 sible extent, it is necessary to have an intimate acquaintance with 

 the structure of each of the layers of the seed-coats, and to be 

 familiar with their appearance when vie wed in different positions. 

 As we have already had occasion to observe, in vegetable 

 powders it is usually the surface view of the various tissues 

 that is presented to the observer, not transverse sections, and 

 experience teaches us that to become thoroughly acquainted 

 with the anatomy of a crude drug it is necessary to examine 

 radial and tangential as well as transverse sections. 



One of the best methods of studying the structure of a seed 

 consists in separating the various layers as much as possible 

 from one another and ascertaining the shape and arrangement 

 of the cells of which they consist, not only on the convex 

 surfaces of the seed but also in the grooves near the apex, the 

 base and the raphe". Examined in this way a variety in form 

 and in anatomical detail will be disclosed that a transverse 

 section would have left quite unsuspected. The study of 

 the illustrations that accompany our descriptions will amply 

 justify our statements. 



We have usually found one of the following processes very 

 successful in disintegrating the coats of a seed. Bather thick 

 transverse sections are made and boiled in water made alkaline 

 with solution of potash. The sections are then mounted on a 

 slide under a coverslip and examined ; the finger is next firmly 

 pressed on the coverslip, and at the same time sliding it a little 

 along, so as to separate the various layers that have been 

 loosened by the boiling in alkali. 



Good results may also be obtained by simply separating the 

 seed-coats from the kernel, soaking them for an hour or two in 

 solution of potash, and then teasing them out with dissecting 

 needles. In the case of very resistant layers that cannot be 

 disintegrated by either of these methods, recourse may be had 

 to maceration with nitric acid and potassium chlorate ; after 

 such treatment they will seldom fail to separate into their con- 

 stituent cells. 



Whichever method is adopted, it must be borne in mind that 

 it is merely supplementary of sections in various directions. 

 The latter are particularly necessary in order to avoid any 

 error due to the action of the alkali on the cell-walls or to 

 ensure that correct relative positions are assigned to the various 

 ayers of cells observed. 



