THE GRASS TRIBE. 259 



of organization. But if you will divide it perpen- 

 dicularly with a sharp knife, you will then be able 

 to see that it has a most complete and highly de- 

 veloped structure. You will find {fig. 7-) that it 

 consists of a thickish scale (c.) upon which lies a little 

 conical body (a.\ composed of several minute sheaths 

 fitted one over the other ; the scale is the cotyledon, 

 and the conical body the plumule or young stem. At 

 the lower end of the embryo may also be made out a 

 sort of sheath lying within its extreme point (5.) ; it 

 is the rudiment of the root. 



"When the embryo first begins to grow, the coty- 

 ledon (c.) swells a little and attaches itself firmly to 

 the albumen by the whole of its highly absorbent 

 surface : the albumen at the same time softening and 

 becoming partially dissolved by the moisture it has 

 taken up from the soil ; by this means the nutritive 

 matter of the albumen is conveyed into the cotyledon 

 as quickly as it is formed. The food thus poured into 

 the cotyledon by thousands of invisible mouths, causes 

 it to swell and all its parts to lengthen. The radicle 

 (J).) is pushed downwards into the soil on one hand, 

 and on the other the plumule rises upwards into 

 the air ; both these parts are abundantly supplied 

 with the materials of growth by the cotyledon, until 

 the roots have established themselves in the soil, and 

 are able to pump up food for themselves, and for 

 the nascent stem. By the time this happens the coty- 

 ledon has shrivelled up, the albumen is exhausted 

 of its nutriment, aud all these temporary parts cease 

 to exist. 



s 2 



