GRASSES OF IOWA, 87 



ration between the contents of contiguous cells. In the case 

 of starch grains, minute pitted furrows occur. These increase 

 in number until the grains become very irregular, showing 

 large radial clefts. It may be stated in this connection that 

 the embryo acts like a j)arasite. It is well known that the 

 embryo can very readily be removed from the endosperm. 

 Sachs* points out that the embryos of normal plants are of a 

 parasitic nature, and it has been shown by several investi- 

 gators that it is possible to excise the embryo of various seeds 

 and germinate plaats. Thus Van Tieghemf, who discussed 

 the dependence of various parts of the embryo and the amount 

 of dependence of the embryo upon its endosperm. In this 

 work the writer experimented with both albuminous and ex-al- 

 buminous seeds. Among the former corn was used. Van 

 Tieghem reached the important conclusion that the young 

 plant can develop without the aid of endosperm, up to a cer- 

 tain stage. That the nutritive matter of the endosperm can 

 be replaced, up to a certain point, by a paste formed of its own 

 substance, or by the paste containing the predominating sub- 

 stance of albumen. Further experiments were made by 

 Blociszweski, I who demonstrated that the embryo seeds sepa- 

 rated, wholly or in part, from their endosperm or cotyledons, 

 could grow without the aid of the stored-up material of the 

 endosperm or cotyledons, and that assimilation begins, pro- 

 viding that the plumule has the necessary amount of light. 



Now, Brown and Morris succeeded in growing the embryo of 

 barley seeds, when grafted upon the endosperm of other bar- 

 ley se:ds; that these embryos grew as well as others depen- 

 dent on its own endosperm. The foreign endosperm under- 

 went all the usual changes. They succeeded likewise in obtaining 

 a growth of barley germs upon wheat. They concluded that 

 the starch-containing portion of the endosperm is simply a 

 storehouse of dead reserve material, and that it is not vital in 

 any sense of the word. 



Time required for germination. — We may next inquire what 

 time is required for germination. Nobbe,§ in his admirable 

 work on seeds, states that seeds of cereals and clovers in gen- 

 eral require 10 days. Melilotus alba, Avena, beets, Cucurbi- 

 taceae, grasses (excepting Phleum, which germinates in ten 



♦Physiology of Plants. 373. 



+Ann. des Scl. Nat. V. 17: 205. 



tLandw. Jahrb. 5: 14. Abst. Jahr. d. Agr. Chem. 1875: 232. 



§Handbuch der Samenkunde. 511. 



