374 TRANS. ST. LOUIS ACAD. SCIENCE. 



5. According to the presence or absence of peripheral bast- 

 bundles : 

 ^ a. Without bast-bundles : Llacusiris, I. pygmaa, L Tuckermani^ 



L echinospora^ L saccharata, L Bolanderi^ I. riparia^ and 7. mela- 



nospora, 



b. With bast-bundles: 7. Engelmanni^ L Hoivelli^ L jftaaida-^ 7. 



melanopoda^ 7. Butkri, 7 Nutiallii^ and 7 Cubana. 



The comparative size or the sculpture of the spores, and the 



number and length of the leaves, furnish no legitimate grounds 



for classification ; still it may be mentioned here, that the largest 



macrospores (0.45 to 0.80 mill, in diam.) are found in IJacusiris^ 



7 Biitleri^ and 7 riparia ; the smallest (0,35 to 045 mill.) in 7 



Jlacczda 



200 



Nittiallii 



est number, 5 to 20, in I.pygmmi^ 7 melanospora^ I. saccharaia^ 

 and 7 Bolanderi. 



The longest leaves (15 to 35 inches long) vsre meet with in 7 



fiaccida, 



/■ 



to 3 inches 



The following classification of our species is proposed as the 

 best I can find, though by no means a faultless one. 



I. Trunk bilobed. 



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



few or many stomata and without peripheral bast-bundles; velum in- 

 complete. 



1. /. lacu$trh, 2. /. pygmcea, 3* /. Tuckermani, 4. /- 

 echinospora, 5. /. Bola7ideru 



B. Amphibious species with abundant stomata in the quadrangular leaves. 



* Without peripheral bast-bundles (these are intermediate be- 



tween the submerged and the truly amphibious species.) 



t Velum partial. 



6. /. saccltarata* *j, /. riparta, ^ 



f I Velum complete. 



8- /. melanospora, 



* * With peripheral bast.bund[es. 



t Velum partial. 



9. /. EngelmannL 10. /. Hovjelli, 



t t Velum complete. 



11. /. flaccid a. 



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



stomata and peripheral bast-bundles in the nearly triangular leaves. 



* Velum partial or almost wanting. 



12, /. melanopoda^ 13. /. Buthri. 



