1890.] 



the Seed of the Castor- oil Plant. 



147 



The work embodied in this paper deals (a) with the agencies which, 

 during germination, render the reserve materials available for the use 

 of the embryo, (b) with the forms in which these are absorbed by it 

 and the mode of their absorption, and (c) with the parts played in the 

 process by the endosperm and the embryo respectively. 



1. The agencies at work. — A ferment is found to exist as a zymogen 

 in the resting seed, which is readily developed by warmth and weak 

 acids into an active condition. .The results of its activity are the 

 splitting up of the fat with formation of glycerine and (chiefly) 

 ricinoleic acid. Further changes, brought about by the protoplasm of 

 the endosperm cells, form from the latter a lower carbon acid which, 

 unlike ricinoleic acid, is soluble in water and is crystalline. These 

 changes do not take place in the absence of free oxygen. A quantity 

 of sugar also is formed, which appears to have the glycerine as its 

 antecedent. 



The proteids of the seed, which consist of globulin and albuinose, are 

 split up by another ferment, with formation of peptone and asparagin. 

 This ferment resembles closely the ferment previously described by 

 the writer as occurring in germinating lupin seeds. 



2. The forms in which the reserve materials are absorbed. — Exam- 

 ination of the seeds during the whole course of absorption shows that 

 the only prodncts which enter the embryo are a crystalline acid, 

 sugar, possibly some peptone, and asparagin. Consideration of the 

 structure of the cotyledons, which are the absorbing organs, shows 

 that the mode of absorption is always dialysis, a view antagonistic to 

 that of Sachs, who has put forward the idea of a penetration of the 

 cell walls by the unchanged oil. It follows from this that the starch 

 seen by him and other observers in the tissues of the young embryo 

 was the result of a re-formation from the diffusible bodies now 

 traced. 



3. The relative influence of the endosperm and the embryo. — The 

 changes are found to be initiated in the endosperm, for they take 

 place, though more slowly, when the embryo is carefully removed. 

 The latter has, however, an influence upon the process, germination 

 being more rapid when it, or even part of it, is left in contact with 

 the endosperm. This is shown not to be due to simple removal of the 

 products of the decompositions, but is rather to be regarded as due to a 

 stimulus of a physiological nature caused by the commencing develop- 

 ment of the embryo. 



4. An additional point of interest in the progress of the germination 

 is the liberation in the endosperm of a rennet ferment of considerable 

 vigour. At present an explanation of the action of this is difficult, 

 though experiments are still proceeding with a view to clearing it up. 



VOL. XLVII. 



M 



