447 
of the Endosperm during Germination. 
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 °/ o 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 liber 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. 
