On Azolla and Salvinia, 273 



20. Vertex of the (yellow) sac of the same. 



21. Another surface of the same, intended to represent the 



cellular appearance. 



PI. xx. 



(Salvinia verticillata and cucullata, the completion of the development of 

 the spherical mass-containing secondaries, and the perfect state of the 

 (yellow) sac- containing secondary capsules of the first species.) 



Fig. 1. 2. Spherical mass-containing secondaries at the time 

 when the trifacials become contained in grumous 

 projections from the inner surface of the secondary 

 capsules, which projections subsequently coalesce 

 into a mass. 



3. Salvinia verticillata, (natural size.) 



4. Capsule containing the indefinite, simply pedicellate, 



spherical, mass-containing secondaries. 



5. The same opened naturally. 



6. Some of the secondary capsules and part of the re- 



ceptacle. 



7. Superficial view of one of the secondaries. 



8. Another view of the same ; centre in focus. 



9. Portion of the secondary capsule, shewing the separa- 



tion of the component cells. 



10. A mass. 



1 1 . The same under pressure, to shew the imbedded trifacial 



cells or spores. 



12. A nearly mature sac-containing secondary capsule. 



13. Contents of the same. 



14. Another view, shews the central attaching (?) process 



between the lobes of the vertex. 



15. Same, (vertex in view,) lobes somewhat displaced to 



shew the trilineal mark. 



16. Mature capsule. 



17. Same, long section. 



18. Contents of the same. 



19. Contents of one of its secondaries. 



20. Cross section of the same. 



21. Salvinia cucullata, natural size. 



All the figures, (with a few exceptions mentioned,) more or less mag- 

 nified : reduced for the most part from (measured) sketches made un- 

 der |, 1-lGth objectives of an achromatic microscope, by Ross. 



