65 



<&ngtual Mvtitlt*. 



A SYNOPSIS OF THE SPECIES OF ISOETES. 



By J. G. Baker, F.B.S. 



In the present paper I have attempted to draw up short com- 

 parative descriptions of all the known species of Isoetes. The 

 genus has been studied very carefully during the last twenty years 

 by A. Braun, Durieu, Engelmann, and Milde ; but their papers 

 are very widely scattered, and often difficult of access. We hoped, 

 as in the case of Characea, that A. Braun would have published a 

 general monograph of the genus, but this he did not live to accom- 

 plish. A few years before his death he worked up all the Kew 

 specimens, and since that we have received a rich addition from 

 the herbarium of Gay, so that I have had authenticated specimens 

 to examine of nearly all the Old World forms that have been 

 named and described, although for some of them the material has 

 been too scanty to allow me to characterise them as fully as I 

 could have wished. For the North American forms our material 

 in London is less complete ; but Dr. Engelmann, who has a mono- 

 graph of them just ready, has kindly helped me with them by 

 letter, and I have implicitly followed his lead. 



KEY TO THE SPECIES. 



Group 1. Aquatics. 

 Veil none. 1. /. triquetra. 2. I. Gannii. 3. I. elatior. 



Veil partial. 4. 7". lacustris. 5. 1. echinospora. 6. I. azorica. 



7. /. pw/mwa. 

 Veil complete. 8. I. Stwwtii. 9. 1. Lechleri. 



* 



Group 2. Subaquaticje. 



North American species, with a 2-lobed rootstock. 



Veil partial. 10. I. Bolanden. 11. /. Tuckermani. 



12. J. saccharata. 13. I. ripariu. 



Veil complete. 14. I. melanospora. 



Australian and New Zealand species, with a 3-lobed rootstock. 



15. I. Muelleri. 16. I. Kirkii. 17. I. alpina. 18, I. Drummondii. 



Group 3. Amphibia. 



Rootstock 2-lobed. (All North American species). 



Veil partial. 19. I. Butleri. 20. I. mslanopoda. 21. I. Engdmanm. 



Veil complete. 22. L NuttaUU. 23. I.fiacmda. 

 Rootstock 3-lobed. (Species of the Mediterranean region). * 



Veil none or very narrow. 24. 1. setacea. 25. J. adqpena. 



26. /. Malinccmiana. 



* 



N -s. vol.9. [Maech, 1880.] * 



