400 XXIX. THE GYNCECIUM OF ANGIOSPERMS. 



commonly in Kanunculaceae, the two integuments of the ovule are 

 blended together. 



Embedding in* Glycerine-jelly, and in Celloidin. In order to 

 prepare sections of the ovule of Aconitum, we can separate 

 one from the ovary, and cut it between the thumb and fore- 

 finger, in the method already known to us. If the ovule is 

 correctly arranged between the fingers, we shall in this way 

 more rapidly obtain true median sections. In this and in other 

 like cases the ovule may, with advantage, be first embedded in 

 glycerine- jelly or in celloidin (celluloidin), and then cut. The 

 glycerine- jelly must be tolerably firm, i.e., must contain a com- 

 paratively large proportion of gelatine. In celloidin only alcohol 

 material can be embedded. We pour the solution of celloidin 1 

 into a small box made of writing-paper, and immerse the ovule in 

 it. The celloidin is then allowed to stand in the air till it has 

 acquired a firm skin, when it is laid in 82 per cent, alcohol. Here 

 after some hours, it acquires the consistence of cartilage, remaining 

 transparent. Celloidin and object are cut together, and the sec- 

 tions laid in glycerine or glycerine-jelly, without its being necessary 

 to remove the celloidin. The sections can be stained with carmine 

 or with logwood (haematoxylin), but not with aniline colours, as 

 these latter colour the celloidin as well. If the celloidin has been 

 procured in cakes, it must be dissolved before use in equal parts of 

 ether and absolute alcohol. In order to make ovules which are to 

 be embedded in glycerine- jelly or in celloidin still more visible, they 

 can be previously stained with watery logwood ; the ovules must 

 then, however, after previous washing in water, be again dehy- 

 drated in absolute alcohol, before being placed in the celloidin. 

 Objects which, in order to make them available for section-cutting, 

 must be permeated with -eelloidin, are first treated with dilute 

 solution of celloidin, in which the object must lie often for days 

 before it is transferred to, and embedded in, the thick celloidin 

 solution. Other methods of embedding will be found described in 

 Chapter XXXII. 



Embryo-Sac of Monotropa. We will now take in hand the 

 study of the interior of the embryo-sac. The most favourable 

 object for this is Monotropa Hypopitys, the Bird's-nest Eape, 



1 To be obtained of Dr. Griibler, in Leipzig, Dufour-strasse, 17. In cakes 

 at about 3s. each, or in solution at 11s. the kilogramme. Also of Messrs. 

 Southall Bros. & Barclay, manufacturing chemists, Birmingham. [Eo.] 



