DICOTYLEDONS PEA AND CASTOR 55 



a short axis, smooth and pointed at one end which is 

 to become the radicle and having at the other end 

 a bud. 



The seed coat is folded in between the radicle and 

 the cotyledons, so that there is as it were a separate 

 pocket for it. The bud of the Broad-bean or Pea 

 is easily made out, having two or more leaves which, 

 though small, are clearly visible. Those of the Brown- 

 bean and Gram are not so obvious, for the leaves are 

 not so far developed; and that of the Melon is still 

 more difficult to distinguish. 



These differences seem to be connected with the 

 amount of food the cotyledons can supply, and the 

 consequent rapidity with which the young plant can 

 develop. 



5. Now look at the Castor seedlings. The first sign 

 of the young plant just as it was in the case of the 

 Brown-bean, Gram and Melon, is an arched hypocotyl 

 which draws after it through the soil two flat cotyledons ; 

 these spread out to the light and turn green. Between 

 them is the bud of the shoot, and as the other leaves 

 appear, notice again how different they are in every way, 

 except colour, from the cotyledons. If the seeds have 

 not been buried deeply you will often find on the coty- 

 ledons, and at first closing over their ends a slimy yel- 

 lowish substance, which if left on gradually dries up 

 till scarcely thicker than a piece of paper, and then falls 

 off. As the cotyledons have come out of the seed, 

 this slimy . substance must have done so also, and to 

 find out what it is, we must examine the seed. 



Unlike the Bean, Gram and Melon, the Castor-seed 

 swells very little in water, the coat being very hard. 



