AZOLLA AND SALVINIA. 



535 



cells are separable ; it contains a large, single, whitish body 

 of a chalky embossed aspect, without any obvious attachment ; 

 this is of an oblong shape, and has a rugose or irregular surface, 

 (PI. CXXIII. Fig. IIL,c.) The upper end, which is rather the 

 smallest, presents three connivent valvular lobes. This 

 white body is the incrustation, it is of a thick, apparently 

 not organic, crustaceous substance. Its lower two-thirds 

 are occupied by the yellow sac (PI. CXXII. Fig. III. c, b, d.) 

 which is with difficulty separable entire ; its upper surface, 

 which on drying becomes concave, presents the trifacial line. 

 This sac is filled with a viscid matter, innumerable granules, 

 and irregular globules of oily fluid. A section in the dry 

 state appears solid (PI. CXXIV. Fig. I.,3. ) A few trifacial 

 cells may still often be found between it and the wall of the 

 secondary capsule. 



The mature capsules of both kinds which are almost si- 

 milar in appearance, appear to become irregularly ruptured 

 (PI. CXXIV. Fig. IV.,2.) ; they are covered externally with 

 brown rigid hairs, and present at the top a brown striated 

 mark (the orginal foramen;) (PI. CXXIV. Fig. I.,2.) they 

 consist of two layers, an outer, from which the hairs arise, 

 composed of irregular angular cells of a brown colour, and an 

 inner, thinner, colourless one, united to the outer only along 

 certain lines : this is composed of oblong cells, in which a 

 few greenish mobile granules exist. 



Those containing the fewer oblong bodies are the most 

 numerous, and more oblong, they are solitary and always next 

 the axis ; therefore if only one capsule is developed it will 

 be of this kind, if more than one, it will be the lowest one. 



It will be hence seen that the differences of Salvinia from, 

 Azolla consist in the situation of the organs ; in the absence 

 of an indusium or involucrum ; in the nucleous being in all 

 developed into secondary capsules, in the early appearance 

 of the papillae indicating the future secondary capsules, their 

 unequal size and number, (on which so much depends,) and 

 their being all subsequently developed indiscriminately : in 



