BOTANICAL GAZETTE, 53 



known. The lobing of the trunk, the presence or absence of sto- 

 mata, and the peripheral bast-bundles are noted as furnishing val- 

 uable characters for classification. The rarest patience has been 

 shown in the careful dissection of tissues in hundreds of specimens 

 not in all cases the best. The author advises any one who desires 

 to study the structure of Isoetes to begin with the well known 

 species and fresh specimens. The arrangement of the leaves varies 

 from distichous to even the 21-34 order; their number from 5 or 

 10 to 100 or even 200; their length from i to 1 inch to 1 or 2 feet. 

 The genus contains from 40 to 60 species, North America haying 

 14, with 12 varieties. The systematic arrangement proposed is as 

 follows: 



I. Tkunk bilobed. 



A. Submerged species with quadrangular leaves, without, or in 4 and 5 

 with few or many stouiata" and without peripheral bast bundles; vel- 

 um incomplete. 



I. /. lacustris. 2. I. pygmcea. 3. /. Tuckermani. 4. /. echinospora. 

 6. I. Bolanderi. 



B. Amphibious species with abundant stomata in the quadrangular 

 leaves. 



* Without peripheral bast-bundles (these are intermediate 

 between the submerged and the truly amphibious spe- 

 cies). 



•)• Velum partial. 

 6. I saccharata. 7. /. riparia. 



ft Velum complete. 



8. I. melanospora. 



** With peripheral bast-bundles. 

 f Velum partial. 



9. /. Engelnwnni, 10. /. Rowelli. 



ff Velum complete. 



II. I. flaccida, 



C. Terrestrial species, maturing when entirely out of water, with abund- 

 ant stomata and peripheral bast-bundles in the nearly triangular 

 leaves. 



* Velum partial or almost wanting. 

 12. I. melanopoda. 13. I. Bulleri. 



** Velum complete. 

 14 /. Nuttallii. 

 II. Trunk trilobed. (Numerous stomata and bast-bundles in the quadran- 

 gular leaves; velum partial.) 

 15. /. Cubana. (From Cuba.) 



In regard to geographical distribution the following quotation is 

 made as it may be of service to collectors: 



Only a small part of the North American continent has been well explored 

 for Isoetes, and there, from Massachusetts to the Chesapeake Bay, they appear 

 abundant enough; farther south, and in the whole interior and western part 

 of the continent, they have thus far been found only in a few localities. Some 

 species are quite local, as is the case, also, with many species oi the old 

 world, while others arc widely distributed. Our two northern species are 

 identical with or closely allied to European forms, all the others are quite dis- 

 tinct from such, so that there is scarcely more than a generic analogy between 

 the species of our middle and southern regions with the Mediterranean ones 

 or those of other regions of the globe. 



