70 THE LIFE OF THE PLANT 



be closely attached to the endosperm, or even surrounded 

 by it, but in either case it can be separated from it 

 without being injured ; this is why albuminous seeds 

 are the best specimens for the study of the nutritive 

 phenomena of the embryo. In grasses the endosperm, 

 originally dry and farinaceous, becomes less dense on 

 germination, till it resembles gruel or milk. Meanwhile, 

 the outer cells of the scutellum, the part of the embryo 

 adjacent to the endosperm (m in fig. 21, b, d, e), grow 

 out as papillae into the softened endosperm, and absorb 

 the nutrient solution from it. The embryos of buck- 

 wheat and of many other plants find themselves under 

 still more favourable conditions. They simply swim 

 in the semi-fluid mass of the endosperm, and absorb the 

 nutrient substances with their entire surface. If in 

 such seeds we remove the embryo from the endosperm, 

 it will stop growing ; but its development can be 

 maintained artificially if, after removing it from the 

 endosperm, we enclose it within a lump of dough made 

 of flour or starch. That the embryo obtains its food 

 from the dough is shown not only by its successful 

 development, but also by the signs of decomposition in 

 the grains of starch in the immediate neighbourhood of 

 the embryo. 



We have several times spoken of the embryo absorbing 

 the nutrient substances from the cotyledons or the 

 endosperm, but evidently this is only a metaphorical 

 expression, and the translocation of the nutrient sub- 

 stances into the embryo has to be explained on the 

 basis of the general phenomena of diffusion, which were 

 studied in our last lecture. We have seen that during 

 germination every nutrient substance passes into a 

 soluble form ; and these solutions, according to the laws 

 of diffusion, have to distribute themselves equally in all 

 parts of the seed, including the embryo. The part played 

 by diffusion ends, however, with this equal distribution 

 of substances, and the attainment of equilibrium. 



