MA RSI LEA. 505 



1. Long section of young involucrum. 

 j. Portion of theca. 



Marsilea, PI. CXV. [continued,) 



B. Male ? body, shewing the nucleus with its mucilagin- 

 ous coats separated, and granular matter with cells imbeded, 

 this is situated between the middle and outer envelopes. 



J. Body. 



2. The same under pressure. 



3. Portion of paries of nucleus. 4. Portion of its con- 

 tents. Corresponds to 1, 2, 3, 4, PI. CXIV. 



5. Below 9. Sporale burst. 6. Ditto to shew the inner 

 sac. 7« Below 6. Sporuia, compound, not separated. 



7\ Male body less developed. 1*. Nucleus and middle 

 coat separated. 2. 2. Male body under pressure. The nucleus 

 is in its earlier periods of developement. 



11. Young involucre, a. portion of a sorus ; b. Male and 

 young theca. 



12. Portion of a sorus ; o s young theca, with a portion 

 of its contents, parent cell already divided ; b. male body, 

 and portion of contents. 



13. Do. more advanced ; a. theca and contents ; b. male 

 body and contents. 



14. a, Theca, and contents ; b, male body ; c, ditto under 

 pressure ; d, portion of contents. 



15. Male body, nucleus scarcely separable. 



16. Young fronds. 



17- o> Male body, corresponds to 15; b, sporuia not se- 

 parated. 



IS. a, Male body ; b, theca ; c, sporuia not yet separated. 

 In Marsilea the general theca is obviously a modification of 

 the frond ; it is formed from one ? conduplicate leaf, the mar- 

 gins of which are united. 



The structure of this is coriaceous outside, internally of 

 green fleshy cellular tissue, this being the only part provided 

 with vessels ; this tissue is perhaps at first solid : but by the 



3 R 



