RESERVE CELLULOSE. 25 



Tliu thickening is first nt the coniL-rs of the cells, as in Iris. The nucleus is in most 

 cases in contact with the walls, imbedded in protoplasm, which is lull of oil globules and 

 grannlar matters. PI. (3, fig. 5, is a sketch of the endosperm at this stage of develop- 

 ment; n, nnclens ; a, thickened corners. 



The addition of water does not canse any noticeable swelling in the reserve cellu- 

 lose, but chloral hydrate does. Iodine stains the reserve cellulose the characteristic 

 brown from the first. When the thickening has proceeded farther, the cell walls pre- 

 sent the appearance seen in PI. (i, fig. 0, which is from a different [)art of the section 

 from which fig. 5 was made. Tiie reserve cellulose is laid down regularly and evenly 

 on the walls, and the canals are already visible. 



In the layer of cells which bounds the circnmference of the endos])erm, no thicken- 

 ing of the wall has taken place. In these cells are starch-builders, and a few minute 

 grains of starch; the protein matters become quite red-brown, when iodine is added. In 

 the presence of minute grains of starch in the starch-builders the seeds differ from Iris, 

 as in two other particulars ; i. e., the absence of the power of swelling with water, which 

 the reserve shows, and the absence as well of the close-set cells, containing oil, which 

 are found in the integument. 



No starch appears later in the ])rocess of maturing of the seed in any of the cells 

 of the endosperm. 



The thickening of the walls continues regularly, always associated with an abun- 

 dance of oil in the cells. 



iVb/e-s 071 otlicr seeds. 



Aspanujus officinalis. Seeds of this plant on July 15 were still very young, and 

 the endosperm was not entirely filled out, but the cells formed contained sugar, though 

 no oil. 



Somewhat later, oil appeared in the seeds in considerable amounts. Before any 

 thickening of the walls took place, starch-builders with minute starch grains appeared 

 in the cells between the chalaza and the center of the seed. In later stages as in Poly- 

 gonatum this disappeared, and no more was formed as the seed ripened. 



Paris quadrifolia of May 18 contained abundant masses of starch in tlu' integu- 

 ments of the seed, though the endosperm cells had only just completed the cell-building. 

 Later, starch appears in the cells of the endosperm. Seeds, not (piite rijie, show a swell- 

 ing of the reserve cellulose, when water is added, though it is never carried so far that 

 the structure is lost. Compare PI. 1, figs. 8 and 9, which show cells of Paris with and 

 without water. 



