796 REPORT— 1902. 



perisperm. The nourisbnieDt has been held to he practically ready for its use, 

 needing only a certain amount of enzyme action to be applied to it to convert the 

 food store from the reserve to the nutritive condition. We have recognised here 

 starch, proteids, and glucosides, and have ascertained that the embryo can 

 furnish the appropriate enzymes for their digestion. Each reserve store has 

 apparently been quite independent of the rest, and the embryo has had control of 

 the whole. 



Certain considerations, however, lead us to the view that for albuminous seeds 

 at any rate this mode of looking at the matter is no longer satisfactory. We may 

 first ask how far the embryo is the controlling factor in the digestion. Putting 

 the matter in another form, is the influence of the parent plant lost when a stable 

 store of food has been provided for the offspring, and does it leave its utilisation 

 ■entirely to the latter .!^ Is the gametophyte prothallus merely to become a dead 

 or inactive structure as soon as it has developed its young sporophyte, or may its 

 influence extend for the longer period of germination ? There are many reasons 

 for thinking this is the case. Indeed the view has been put forward by some 

 observers at intervals for some years. Gris claimed to have shown it in 1864 ; 

 but it was opposed by Sachs, who said that the enzymes which cause decompo- 

 sitions in the reserve materials are always formed in the young plant or embryo 

 and are excreted by the latter into the endosperm. Some careful experiments on 

 the point were conducted by Van Tieghem and were published by him in 1877. 

 His work was carried out on the seeds of the castor-oil plant. He deprived the seeds 

 of their embryos and exposed them for some weeks on damp moss to a temperature 

 of 25-30° C. After several days of this exposure he found the isolated endosperms 

 were growing considerably, and at the end of a month they had doubled their 

 dimensions. In the interior of the cells he found the aleurone grains to be 

 gradually dissolving, and the oily matter to be diminishing, though slowly. 

 The dissolution extended throughout the mass of the endosperm, and was not 

 especially prominent in the side that had been nearest to the cotyledons. He 

 noted, too, that though starch did not normally appear in the germinating endo- 

 sperm, under the condition of non-removal of the products of the decomposition, it 

 •did appear in the cells in the form of small grains, though not till after several 

 days had elapsed. Van Tieghem also observed that the progress of the decom- 

 positions could be arrested and the endosperms made to reassume a quiescent 

 condition, and that then the aleurone grains again became formed, though in less 

 quantity than before. 



In some experiments on Ricinus which I carried out in 1889 I found much the 

 same sequence of events as Van Tieghem had described. The endosperm 

 unquestionably became the seat of a renewed metabolism, in the course of which 

 many interactions between the various reserve materials became noticeable. It 

 was remarkable that the activity of this metabolism was much more pronounced 

 ■when the embryo or parts of it were left in contact with the endosperms. 



An observation of a similar character has been made by Haberlandt and by 

 Brown and Morris in the case of the seeds of grasses. The conversion of the 

 reserve cellulose of barley grains has been shown by these observers to be the 

 result of the action of an enzyme cytase, which is secreted largely by the so-called 

 aleurone layer, which is found surrounding the endosperm, immediately underneath 

 the testa. 



Recently my own work has been bearing on this question, particularly as 

 regards the behaviour of the seeds of Ricinus during germination. The reserves 

 of this seed are mainly composed of oil and aleurone grains, hardly a trace of 

 carbohydrates being present. At the onset of germination there is a remarkable 

 appearance of both cane sugar and glucose, which increase as the oil diminishes. 

 The old view advanced to explain this fact has been the transformation of the oil 

 directly into the sugars or one of them, a theory which it was difficult to reconcile 

 with the chemical possibilities of oil. I have found that side by side with the 

 appearance of the sugar v/e have also the formation of a considerable quantity of 

 lecithin, a fatty body containing nitrogen and phosphorus. The seed contains a 

 comparatively large amount of phosphorus in the form of the well-known globoids 



