SECT. V. GEMS. 281 



SUBSECTION II. 



The Bulb. Bulbs, which according to the dis- Dissection 

 tinctions instituted in the foregoing book are either 

 radical or caulinary, exhibit in their external struc- 

 ture, or in a part of their internal structure that is 

 easily detected, several distinct varieties, some 

 being solid, some coated, and some scaly ; but all 

 protruding in the process of vegetation the stem, 

 leaf, and flower, peculiar to their species. 



If the solid bud is taken and divided into two Whether 

 halves by a vertical or longitudinal section, it will sc 

 be found to consist externally of a sort of fibrous or 

 membranaceous envelope separable into two or 

 more layers ; and internally of a fine epidermis en- 

 closing a firm but succulent pulp, in the centre of 

 which are lodged the rudiments of the future plant, 

 as in Gladiolus communis and Colchicum autumnak^ 

 in which the several parts of the flower may be dis- 

 tinctly perceived long before the period of their 

 natural evolution. 



If the coated bulb is taken and dissected, it will Coated, 

 be found to be composed of a succession of con- 

 centric layers somewhat resembling a number of 

 hollow spheres gradually diminishing in size from 

 the circumference to the centre, and enclosed with- 

 in one another. The exterior layer consists some- 

 times of a fine and delicate membrane, as in the 

 Onion ; or of a thick and leathery coat, as in the 

 Tulip, forming a sort of envelope to the bulb ; and 



