374 ] TRANS. ST. 1 . 0 VIS ACAD. SCIENCE. 
5. According to the presence or absence of peripheral bast- 
bundles : 
a. Without bast-bundles : 7 lacusttis , 7 pygmcea , 7 . Tuckermani, 
I. echinospora , 7 saccharata, I Bolanderi , 7 riparia , and 7 . 2^/0- 
nospora . 
3 . With bast-bundles : 7 Engelmanni , 7 Howelli , I. jlaccida , 7 ". 
melanopoda , 7 . Butleri, I. Nuttallii , 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 7. lacustris , 
7 Butleri , and 7 riparia ; the smallest (0.25 to 0.45 mill.) in 7 
melanopoda , 7 Jlaccida, and 7 Engelmanni var. valida. 
The largest number of leaves, 50 to 200, are observed in the 
last mentioned form, in 7 . melanopoda and in 7 Nuttallii; the small¬ 
est number, 5 to 20, in 7 pygmcea , 7 melanospora , 7 saccharata y 
and 7 , Bolanderi . 
The longest lq^ves (15 to 25 inches long) we meet with in 7 . 
Engelmanni , 7 Jlaccida, and 7 Cubana; the shortest (£ to 3 inches 
long) in I.pygmm, 7 melanospora , and 7 saccharata . 
The following classification of our species is proposed as the 
best I can find, thpugh by no means a faultless one. 
I. Trunk bilobed. 
A - !&t 
7 - rac “- «•* 
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