Chap. II. BREAKIN& THROUGH THE GROUND. 87 



root-stocks, &c., buried beneath tbe ground, the surface 

 is broken by a cone formed by the young imbricated 

 leaves, the combined growth of which gives them force 

 sufficient for the purpose. 



With germinating monocotyledonous seeds, of 

 which, however, we did not observe a large number, 

 the plumules, for instance, those of Asparagus and. 

 Canna, are straight whilst breaking through the ground. . 

 With the Graminese, the sheath-like cotyledons are 

 likewise straight ; they, however, terminate in a sharp 

 crest, which is white and somewhat indurated ; and this 

 structure obviously facilitates their emergence from 

 the soil : the first true leaves escape from the sheath, 

 through a slit beneath the chisel-like apex and at 

 right angles to it. In the case of the onion {Allium, 

 cepa) we again meet with an arch ; the leaf-like coty- 

 ledon being abruptly bowed, when it breaks through 

 the ground, with the apex still enclosed within the; 

 seed-coats. The crown of the arch, as previously 

 described, is developed into a white conical pro- 

 tuberance, which we may safely believe to be a 

 special adaptation for this office. 



The fact of so many organs of different kinds— 

 hypocotyls and epicotyls, the petioles of some coty- 

 ledons and of some first leaves, the cotyledons of 

 the onion, the rachis of some ferns, and some flower- 

 stems — being all arched whilst they break through, 

 the ground, shows how just are Dr. Haberlandt's * 

 remarks on the importance of the arch to seedling, 

 plants. He attributes its chief importance to the 

 upper, young, and more tender parts of the hypocotyl. 



♦ ' Die Sohutzeinriohtunpren in though our observations lead us 



liler Eutwickeluug dtr Keirn- to difter on soaie points from tho 



pdanze,' 1877. We have learned author. 

 much irom this interesting essay, 



7 



