STRUCTURE AND GERMINATION OF SEEDS 27 



unusual occurrence (6). As the roots of these seedlings 

 grow they become covered with a rich crop of root-hairs 

 (r.h). Notice carefully how they are distributed, and from 

 what part of the root they are absent. 



Seeds of the Edible Pea, Sweet-Pea, Vegetable Marrow, 



Fig. 11. Seedlings of Mustard and Cress. 1, section of 

 Mustard-seed showing the folded cotyledons ; 2, 3, 4, and 5, different 

 stages in germination of Mustard-seed ; 6, Cress seedling ; 7, root- 

 hair, magnified ; c, cotyledon ; c.w, cell-wall ; e, epidermal cell ; 

 hy, hypocotyl ; n, nucleus ; P, protoplasm ; pi, plumule ; r, section 

 of radicle ; ra, radicle ; r.h, root-hair ; s, seed ; s.r, secondary root ; 

 /, testa. 



fruits of the Sunflower, Common Ash, Sycamore, and Oak, 

 should be germinated in the same way and their modes of 

 growth compared. In the case of the Sunflower (see 

 Fig. 22), note that when the radicle emerges, the fruit-coat 

 splits into two halves along the edge and, unlike the Bean, 



