SEEDS. 9 



form of fatty oil; the other nitrogenous, in the form of aleurone. 

 We shall find the same association of nitrogenous and non-nitrog- 

 enous food substances in other seeds. 



IX. Prepare sections of the endosperm of a flax seed, 

 and, as before, examine some in glycerine and others in 

 water. How do the aleurone grains compare in size, form, 

 and structure with those of the castor oil seed? 1 



X. Make a transverse section of a grain of wheat that 

 has lain in water a few hours, cutting it in such a way that 

 the section will show the coats of the grain and a portion 

 of the endosperm. Mount in water. Notice 



1. The large cells making up most of the endosperm. 



What do they contain? 



2. Outside of these a layer of cells, rectangular in sec- 



tion, containing aleurone. 



3. The behavior of the substances contained in the 



different cells when iodine is applied. Draw a 

 portion of the section. 



4. The arrangements for protection of the embryo, 



together with its food supply, by means of the 

 united fruit and seed-coats. [The former consists 

 of several layers of cells with strongly thickened 

 walls, the latter of two very thin layers imme- 

 diately outside the cells that contain aleurone. 

 Tangential sections treated with sulphuric acid, 

 compared with the transverse sections, will make 

 the structure plain.] 



XL Record in full what you have ascertained regarding 

 reserve materials and their storage in seeds. What are 

 the different kinds of non-nitrogenous food substances thus 



1 Cf. Frank, Lehrbitch der Pflanzenphysioloyie, p. 158. 



