SECTION 3.] 



SEEDLINGS. 



15 



Section III. MORPHOLOGY OF SEEDLINGS. 



18. Having obtained a general idea of the growth and parts of a pha- 

 nerogamous plant from the common Flax of the field, tlie seeds and seed- 

 lings of other familiar plants may be taken up, and their variations from the 

 assumed pattern examined. 



19. Germinating Maples arc excellent to begin with, the parts being 

 so much larger than in Flax that a common magnifying glass, although 

 convenient, is hardly necessary. The only disadvantage is that fresh seeds 

 are not readily to be had at all seasons. 



20. The seeds of Sugar Maple ripen at the end of summer, and germi- 

 nate in early spring. The em- 

 bryo fills the whole seed, in 

 which it is nicely packed ; and 

 the nature of the parts is ob- 

 vious even before growth begins. 

 There is a stemlet (caulicle) and 

 a pair of long and narrow seed- 

 leaves (cotyledons), doubled up and coiled, green even in the seed, and in 

 germination at once unfolding into the first pair of foliage-leaves, though 

 of shape quite unlike those that follow. 



21. Red Maple seeds are ripe and ready to germinate at the beginning o£ 

 summer, and are therefore more convenient for study. The cotyledons are 

 crumpled in the seed, and not easy to straighten out until they unfold them- 

 selves in germination. The story of their development into the seedling is 

 told by the accompanying Fig. 14-20 ; and that of Sugar Maple is closely 

 similar. No plumule or bud appears in the embryo of these two Maples 

 until the seed-leaves have nearly attained their full growth and are acting 

 as foliage-leaves, and until a root is formed below. There is no great store 

 of nourishment in these thin cotyledons ; so further growth has to wait 

 until the root and seed-leaves have collected and elaborated sufficient ma- 

 terial for the formation of the second internode and its pair of leaves, 

 which lending their help the third pair is more promptly produced, and 

 so on. 



22. Some change in the plan comes with the Silver or Soft White Maple. 

 (Fig. 21-25). This blossoms in earliest spring, and it drops its large and 

 ripened keys only a few weeks later. Its cotyledons have not at all the 

 appearance of leaves ; they are short and broad, and (as there is no room 

 to be saved by folding) they are straight, except a small fold at the top, — 

 a vestige of the habit of Maples in general. Their unusual thickness is due 



Fig. 11. Embryo of Sugar Maple, cut throiigli lengthwise and taken out of the 

 seed. 12, 13. Whole embryo of same just beginning to grow; a, the stemlet or 

 eaui'cle which in 13 has considerably lengthened. 



