448 Messrs Gardiner and Hill, The Histology 



the shorter end walls one large group of threads occurs, which 

 occupies the whole of the wall 1 (Fig. 3). Thus, though the walls 

 are unpitted, the connecting threads are arranged in groups. If 

 sections of a young germinating seed are examined the cotyledon 

 is seen to have increased in size, and abundant evidence of enzyme 

 action is afforded by the partially broken-down walls of the 

 surrounding endosperm cells. 



A careful examination of the walls of the cells in the imme- 

 diate vicinity of the cotyledon, which walls moreover are crowded 

 with threads, shews that the ferment effects an entrance by only 

 a few of the threads, and, proceeding from the interior of the cell 

 outwards, works along them towards the middle lamella, where it 

 quickly becomes more active and rapidly dissolves the reserve 

 cellulose in the neighbourhood of the lamella, thereby forming 

 large cavities broadly fusiform in shape, which shew their broadest 

 diameter at the lamella, and taper away to the edge of the wall on 

 either side 2 (Fig. 8 (y)). 



In this region, owing no doubt to the mucilaginous character 

 of the lamella and adjoining layers of the wall, the enzyme is more 

 vigorous and effective than on the younger and more horny layers 

 of the cell membrane. As the ferment action proceeds these 

 cavities break into one another, and so the whole wall becomes 

 disorganized and in its altered and mucilaginous condition now 

 stains with the dyes employed for demonstrating the ' connecting 

 threads.' The tracks of the threads can, however, still be seen 

 after the cell walls have become disorganised (Fig. 8). 



If sections of a seed are examined, which has been allowed to 

 germinate for a longer period and in which the cotyledon has 

 enlarged so considerably inside the seed as to have displaced the 

 greater part of the endosperm, it is found that the ferment attacks 

 the cell walls of the more peripheral portions of the endosperm in 

 a somewhat different manner to that just described, for whereas 

 we have shewn that the ferment dissolves the walls of the rounded 

 cells at the centre of the seed, more particularly in the region of 

 the lamella, in the older walls it commences its attack at the inner 

 or free edge of the wall, and proceeds outwards, in a V-shaped 

 manner towards the middle lamella (Fig. 9). These differences in 

 the method of the ferment action on the cell walls appear to be 

 due to some differences in the composition of the 'reserve-cellulose' 

 in different parts of the endosperm. 



The amount of endosperm tissue undergoing dissolution at any 

 given time is comparatively small, since the action of the ferment 

 is localized to the layers of cells immediately surrounding the 



1 Cf. Gardiner, Proc. Roy. Soc, 1897, Fig. 1. 



2 Cf. Hill, Ann. Bot., vol. xv. 1901, fig. 13, PI. XXXII. p. 596. Also Gardiner, 

 loc. cit. fig. 3. 



