Endosperm of Hordeum vulgare during Germination. 19 



in the same manner as desct ibed previously when treating of the in- 

 tact endosperm. 



The results were in no sense doubtful. No visible changes of any 

 kind took place until micro-organisms had established themselves, 

 when dissolution of the cell-membrane commenced. Moreover, 

 there was the strictest possible parallelism, at all stages, between 

 the " dead " and the " living" endospermous fragments, using these 

 terms to express the state, at the commencement of the experiments, 

 of those fragments which had or had not been previously put under 

 conditions for extinguishing any residual vitality which, their cells 

 possessed. In this respect our later experiments have fully borne 

 out the statement of one of us in 1890* that the starch-containing 

 portions of the endosperm are una,ble to originate any visible changes 

 in the reserves which they contain. 



Thus we must conclude that it is to the influence of the "aleurone- 

 layer," and the " aleurone- layer " only, that we must look for those 

 well-marked changes which undoubtedly take place in the endo- 

 sperm when this is separated from its embryo and placed under 

 favourable conditions. 



This is a conclusion differing materially from that of the 1890 

 paper referred to above, which concludes with the following 

 passage : " As far as the evidence goes at present, we are certainly 

 not justified even in suspecting that the cells of the * aleurone-layer ' 

 are glandular in the same sense as are the epithelial cells of the 

 scutellum, and until evidence of a far more convincing nature is 

 forthcoming we must adhere to the opinion that the diastase " (and, 

 we might have added, the cytase also) " accumulated in the germi- 

 nating seeds of the Grasses owes its origin exclusively to the 

 secretory glandular cells forming this scutellar epithelium, and that 

 the aleurone-cells belong solely to the reserve-system of the seed." 



This opinion was justified by the known facts of seven years ago, 

 but certainly requires modification in the light of our more recent 

 experiments. It seems, in fact, quite impossible to understand the 

 results of these later experiments, if we deny the power of the 

 "aleurone-layer" to produce a considerable amount of cytohydro- 

 lytic action on the cell-membrane, and even a certain amount of 

 action on the starch itself. The relative share in the modification of 

 the endosperm-reserves which falls to the scutellum and the 

 " aleurone-layer " respectively in normal germination we shall con- 

 sider presently, but it is in the first place necessary to criticise an 

 important experiment of the 1890 paper, which at the time seemed 

 absolutely conclusive against the view that the "aleurone-layer" 

 has any power of modifying the endosperm-contents. Whilst in- 

 vestigating the best conditions for the development of excised 

 * Brown and Morris, loc. cit. 



