14 GRACE E. COOLEY ON 



consists of <a cotyledon, sheathing the vegetative point ; and of a minute hypocotyl. 

 When a section is made through a seed which has been lying sometime in the soil, 

 but has not yet protruded its radicle, the embryo is seen to be in quite an undeveloped 

 state and no growth has taken place. In section, the embryo is slightly spoon-shaped, 

 consisting almost entirely of the cotyledon which, at its base, sheaths the vegetative 

 cone of the future upward axis. Below this is the tiny hypocotyl bearing a well- 

 developed root-sheath. 



The vascular system is outlined in both cotyledon and hy})ocotyl by nascent 

 tissue. 



The root-cap is strongly marked by the presence of starch, which has appeared 

 in its cells since the seed was put in the ground. 



Starch-builders are detected below the vegetative cone and in tlie cotyledon. 

 Plate 3, fig. 2, shows at A a section of the embryo before growth has taken place ; 

 a, cotyledon ; 6, hypocotyl ; o, vegetative cone ; d, nascent vascular tissue ; e, root- 

 cap. Plate 3, fig. 2, shows at B the region of vegetative cone, more enlarged ; 

 d, cotyledon ; h, nascent vascular tissue ; c, vegetative cone ; «, cells containing starch- 

 formers. 



The cells of the cotyledon contain a good deal of oil in small globules, particu- 

 larly at the apex and in the outer layer of cells, which are in contact with the 

 endosperm. Much of this oil, probably all, has been stored up in the cotyledon cells 

 themselves and was not withdrawn from the cells of the endosperm. When aggre- 

 gated by treatment with chloral hydrate, and stained with osmic acid, the oil j^resents 

 the appearance seen in Plate 3, fig. 2, C. 



When the oil is removed by absolute alcohol, the starch-formers show more 

 clearly, and the presence of minute grains of starch in them can be demonstrated 

 by warming the slide after the iodine has been applied. PI. 3, fig. 2, D, shows a few 

 cells from below the vegetative point, which have been treated with absolute alcohol 

 and iodine ; the starch-formers are apparent. 



Outside the cotyledon, in contact with the endosperm cells. l)ut not in them, are 

 a few oil drops. 



With congo-red the cells of the endosperm take the characteristic reaction of 

 reserve cellulose, coloring with some difficulty but strongly. The cells of the 

 cotyledon show a bluish tendency with congo-red, indicative of the presence of acid 

 in small quantities. With iodine, no difference is detected between the reserve 

 cellulose in this stage, and the resting winter state. 



The only changes, since water was furnished the seed and germination 

 started, are the softening and swelling of the tissues; the possible withdrawal of a 



