RESERVE CELLULOSE. I5 



small amount of oil from the endosperm cells; and the development of starch in the 

 embryo. 



The examination of a young seedling still buried in the ground exhibits a long 

 vigorous root and a short, considerably thickened stem whose cells are gorged with 

 starch. In this we see the beginning of the formation of the rhizome. The small 

 bud has broken away from the sheathing petiole of the cotyledon, but is still little 

 developed. A Y>a.rt of the cotyledon remains in the seed, and has enlarged to half 

 the capacity of the seed, replacing the endosperm. Its petiole grew just enough to 

 carry the hypocotyl and bud out of the seed and then enlarged. 



PI. 3, fig. 3, A, is a view of a young seedling in section, and B is the same 

 enlarged. The section has been treated with iodine ; a, undissolved reserve mateiial 

 of the endosperm to which iodine imparts the characteristic red-brown color; h, endo- 

 sperm cells, from which reserve material has been dissolved and which are unstained 

 with iodine; c, the cotyledon with its vascular system well formed; d, portion of the 

 cot^dedon which carried the bud out of the seed; e, bud which has freed itself from 

 the sheathing cotyledon;/", the stem already thickened and containing starch, i. e. the 

 young rhizome ; g, root-hairs. Comparison with fig. 4, a younger stage of the 

 seedling, will show the manner of extricating the bud from the seed. In this 

 case the cotyledon is curiously lolled, and the sheath is apparent. 



In cotyledons from seedlings of this stage of development, there are short, well- 

 formed spiral vessels in the vascular portions, and the system in the stem and root is 

 well developed. 



The cells which lie in contact with the endosperm contain much oil — a little is to 

 be found in cells in the neighborhood of the vascular portions, but none is to be found in 

 the portions of the seedling which lie outside the seed. 



Starch-formers are to be found in the cells, near the bounding layer of the cotyle- 

 don and near the vessels, and in these minute starch grains may often be detected. The 

 presence of starch in the cotyledon is not constant; sometimes the cells contain consider- 

 able quantities, but always in minute grains. 



The thickened stem and apical bud contain starch in grains, which seem permanent. 



In general the cells of the cotyledon in the seed are rather empty. No sugar is 

 found in the seed, but in the cotyledon outside the seed a little is detected. 



In the endosperm, important changes have taken place. The outer masses next the 

 seed-coats still take the characteristic red-brown color, and are unchanged. Adjacent to 

 these, lie cells whose walls are no longer thickened, and remain colorless under the 

 action of iodine; and farther in, in contact with the cotyledon, are mere shreds of 

 pressed and distorted cell walls. 



