Endosperm of Hordeum vulgare during Germination. 11 



In those cases where comparisons had to be made between endo- 

 sperms treated in different ways the mica-rafts were made to carry 

 twelve corns, the two series of six each being placed on either side of 

 the raft. In this manner there was an exactly equal chance of the two- 

 sets being infected to the same extent by extraneous organisms, an 

 important condition, which often enabled us in a long series of 

 experiments to differentiate changes due to the influence of organ- 

 isms from those due to other causes. Latterly we found these 

 extreme antiseptic precautions unnecessary for the reasons already 

 given, and we also found it undesirable to previously steep the grain 

 before degermation, since the embryo may readily begin to func- 

 tion slightly during the softening process, especially when the 

 temperature is high. In such cases there is a danger of the projec- 

 tion of a small quantity of enzymes from the embryo into the 

 proximal portions of the endosperm, and these enzymes, after de- 

 germation of the grain and the floating of the endosperms on the 

 rafts, may give rise to certain changes in the endosperm which may 

 be \\rongly attributed to a self -digestive power of the endosperm- 

 cells themselves, whereas they have a different origin altogether. 



It is true- that this source of error may be minimised by reducing 

 the period of steeping, and by keeping the temperature of the water 

 low ; but it is much more satisfactory to degerm. the grain whilst still 

 in its dry resting condition, a process which does not present any 

 difficulty. It must, however, be performed with the aid of a lens, sa 

 as to ensure the complete removal of the scutellum and the whole of 

 its limiting epithelial layer. 



If endosperms thus treated are soaked in water for from twenty- 

 four to forty-eight hours, and are then transferred to the perforated 

 mica- rafts in such a manner as to immerse the whole of the depleted 

 layer, we observe the following changes to take place. 



Within two or three days from the commencement of the experi- 

 ment the peripheral, tripartite layer of the endosperm, the so-called 

 " aleurone-layer " (" Kleberschicht "), shows an increasing tendency 

 to separate from the adjacent amyliferous cells. This is noticeable 

 in the first instance at the proximal end of the endosperm, on the 

 dorsal side,* where the " aleurone-layer " is intersected by the 

 " depleted layer," and whilst it is to some extent traceable for some 

 distance round the periphery towards the ventral fold, it extends 

 much more rapidly in a distal direction along the dorsal side. 

 Where there is this megascopic indication of the separation of the 

 ** aleurone-layer," it is always found that the amyliferous cells, 

 immediately underlying, f show indications of change. In the first 



* The dorsal side is that immediately opposite the ventral suture. The terms 

 proximal and distal are used with reference to the position of the embryo. 



f The outermost layer of ihe amyliferous poi'tion of the endosperm consists of 



