PHANEROGAMIA I BUD ORGANS, 



291 



must, on the same principle, have class 4 brown, 5 yellow, 6 red bulbs, 

 &c. ; we must class others, as containing starch, or gum, because their 

 inner scales sometimes contain starch and sometimes gum. In the 

 solid bulbs we have also heard of blending of the coats of the bulb ; a 

 sufficient proof that no one had taken the trouble to analyse the well 

 known examples of bulbus solidus, and to compare them together, much 

 less thoroughly studied the history of development. Each germi- 

 nating bulbous plant has, during the first year, a bulbus solidus (fig. 

 175.) on an infantine scale, because then only the thickened sheathing 

 part of the cotyledonary leaf is present (fig. 175. c). 



175 



176 



Whether a bulb shall later be known as bulbus solidus or bulbus 

 foliosus depends upon the time required before the external sheathing 

 parts begin to die away, and upon the greater or less mass to which the 

 sheathing part enlarges. The distinction is not of vast importance, since 

 in the same genus are found the leafy bulb (Allium Cepa) and the solid 

 bulb (Allium ursinum) (fig. 176.). In families there is little or no con- 

 stancy of this character. I have traced the history of the development of 

 Allium Moli/, acutangulum, ursinum (fig. 176.); Gagea lutea, arvensis ; 

 Hyacinthus orientalis, Lilium pumilum (fig. 175.) ; and Tulipa sylvestris. 

 There is yet another point, which makes the precise definition of a bulb 

 very difficult. If we compare the series of gradations of the bulb from 

 Allium Cepa to Allium Porrum, and from this, through Allium sativum, 

 to the common Monocotyledon bud, especially to that with uninterrupted 

 vegetation, for instance, in Phormium tenax, it will be very difficult 

 to draw a line of distinction, which indeed scarcely seems to exist in 

 nature. 



In treating upon axes and leaves, the most important matters con- 



75 Lilium pumilum. Germination. A, Natural size : a, seed ; b, sheathing part of 

 the cotyledonary leaf; c, the sheathing part exhibiting a small solid bulb ; d, the radi- 

 cle. B, A longitudinal section through the under part of the cotyledon, somewhat 

 enlarged : b, c, d, as in A ; e, the body of the plant (stalk), and foundation of the bud. 

 C, A cross-section through the midst of B : c c, as before ; e, the largest (external) leaf 

 of the bud. 



176 Allium ursinum, natural size. A longitudinal section through the solid bulb, 

 a a, Withered leaf, clothing the bulb as a membrane; b, flower-stalk; c, fresh leaf, 

 whose sheathing part encloses the next year's bud (d), which is the terminal bud of the 

 stem (e), which is continually dying away beneath. 



u 2 



