RESERVE CELLULOSE. 21 



7. In all Mie seeds the cotyledon is tlie ;iu;i'iit of absorption and transfer. In 

 Allium and Iris, a large number of the endosp^'rui cells are also active in transferring 

 the reserve material, and in these cases, all the cells contain protoplasm and oil until the 

 reserve cellulose is exhausted, and then, only, become empty and collapse. 



Development of Reserve Cellulose in the Seed. 



To understand rightly the nature of the reserve cellulose, regard must be had to 

 the phenomena connected witli its appearance during the formation of the seed. 

 Accordingly, fruit-pods of Iris sibirlca, and berries of Polygonatinn 7nuUiflo)'U7n, have 

 been gathered during the formation of the seed, and all the different stages of develop- 

 ment have been followed under the microscope. These observations have been com- 

 bined with a less detailed study of a nundier of other seeds, during the processes of 

 ripening, so that a somewhat full history of the origin and growth of reserve cellulose 

 in the Liliaceae, and its allies, lies before us. 



Growth of (he Seed of Iris sihirlcn. 



Iris sibirlca, on June 20, 1804, four weeks after flowering, had well-developed fruit- 

 pods, with young seeds, which, in many cases, contained well-formed embryos, and 

 endosperm, in which cell division had ceased and the walls were formed. 



The young seeds are flat and green, the immature testa containing much chloro- 

 phyll. 



Next these loose cells of the outer integument lies a, layer of firm, small cells, with 

 no intercellular spaces. Each of the cells in the layer contains a large greenish yellow, 

 oily globule, which half fills it. Two layers of spongy, almost empty, cells lie between 

 these and the endosperm. 



The endosperm cells, when cell-division has ceased, show, in sections made in 

 the plane of the long diameter of the seed, a radical arrangemejit. The small, though 

 perfectly formed, embryo lies at the micropylar end, and opposite, as the ovule is 

 anatropous, the firm irregular cells of the chalaza appear, to which leads the bundle 

 of spiral vessels, which furnishes the path of food communication with the mother 

 plant. 



PI. 5, fig. 1, presents a view of a section of the seed, taken in the plane of its 

 long diameter at this stage of development: a. endosperm; h, end^ryo ; c, layer of 

 cells containing oil drops ; d, chalaza, in whose cells is a little starch ; e, chlorophyll, 

 containing cells of the integument. Though the cells of the endosperm are all 



