EXPLANATION OF THE PLATES. 365 



disappears. The great and essential similarity of this process to that 

 described in the Fern is not to be mistaken. 



F IG . 8. The end of the tube drawn out of the seed-bud, at a 

 later period. The tube c has begun to decay. The little roundish 

 body of the nascent embryo shoots out to the right and left two little 

 knobs, the first-leaves a at the upper end is the beginning of the 

 stem, the opposite extremity becomes the root. 



FIG. 9. The embryo, now almost perfect, extracted from the 

 seed-bud, which by this time is transformed into the seed. The 

 two first-leaves, the seed-leaves or cotyledons, are complete, a and b, 

 and cover the bud which has been formed between them ; this bud 

 is the foundation of the future stem ; at the other end, the root c is 

 also perfect. At this period all vegetative power seems to be 

 exhausted. The ripe seed is thrown off by the plant and lies for 

 a varying length of time on the ground, the embryo within mani- 

 festing no trace of the persistence of life. At last, at the time 

 appointed, germination commences, for an example of which the 

 Flax-plant may serve. 



FIG. 10. Longitudinal section of a Flax-seed. The embryo cut 

 through lengthways is seen to be enclosed in a double coat, and 

 sends out a rootlet (radicle) below, while it ends above in a little 

 bud (plumule) which is contained between two large seed-leaves or 

 cotyledons. 



FIG. 11. A germinating Flax-seed (n. s.) The little plant has 

 burst its coats and is about to throw off its shell. 



FIG. 12. A somewhat later stage (n. s.) The young plant has 

 become perfectly independant and the bud or plumule is beginning to 

 develope into stem and leaves. 



PLATE IV. and the FRONTISPIECE are fully explained in the 

 Fourth and Twelfth Lectures. 



THE END. 



