of the Endosperm, during Germination. 447 



and encroaches upon and displaces the tissue of the endosperm. 

 As we have seen the seedling absorbs the reserve materials con- 

 tained in the seed, but, instead of using them entirely for purposes 

 of growth, re-stores them again in part as starch in the thin- walled 

 epicotyledonary tuber, which very early makes its appearance at 

 the base of the developing cotyledon (Fig. 6). 



In the short sketch of the germination of the seeds of Tamus 

 already given, the relations of the embryo to the endosperm have 

 been briefly described, and we may now proceed to deal with the 

 histology of the endosperm during germination. 



The cells of the endosperm vary considerably in size. Those 

 immediately beneath the testa are' large and elongated in the 

 radial direction, but in the centre of the seed they are much 

 smaller and arranged in an irregular manner. In all cases the 

 walls are unusually thick, and are composed of a hard and horny 

 variety of cellulose, which gives very little reaction with the dyes 

 usually employed for a microchemical examination of the cell wall. 



With watery solutions of both methylene blue and Congo red, 

 only a very slight staining of the walls takes place, and with the 

 former reagent the staining is practically confined to the middle 

 lamellae of the walls of the more peripheral cells of the endo- 

 sperm. In most of the walls a middle lamella is not evident, but 

 it can be distinguished as a fine line in the walls of the loosely- 

 packed and rounded cells in the centre of the seed, and also in the 

 walls of the cells around the embryonic cavity. The cell walls 

 remain practically unstained with safranin, but with a solution 

 of iodine in potassium iodide they are stained yellow, and after 

 the action of iodine solution and sulphuric acid take on a brownish 

 coloration. Sections of the endosperm stain crimson violet with 

 alkali-alizarin, but after being heated with 2 °/ sulphuric acid for 

 two hours they are not stained at all with this reagent 1 . 



From these reactions it seems probable that the walls are com- 

 posed of a reserve cellulose like that described by Gruss from the 

 seeds of Phoenix and other plants, and not of a cellulose compound 

 similar to that of the ordinary cell walls of the plant. 



The connecting threads, which have been briefly described in 

 the communication previously mentioned 2 , occur in small or large 

 groups throughout the walls and shew a well-marked median 

 node at the middle lamella. Towards the periphery of the seed, 

 where the cells are larger than those in the centre and shew 

 distinct end and side walls, the connecting threads are seen to be 

 distributed somewhat differently, for in the longer side walls 

 numerous groups of threads occur scattered at intervals, whilst in 



1 Gruss, " Studien iiber Reserve-cellulose," Bot. Gent., 70, 1897, p. 242. The 

 cell walls of the endosperm of Galium and Phoenix gave a similar reaction. 



2 Gardiner, Proc. Roy. Soc, 1897. 



