6 
ENGELMANN—THE GENUS ISOETES IN N. AMERICA. [363 
1867. In the fifth edition of Gray’s Manual, p. 676, I for the 
first time published 7 . echinospora as an American species, dif¬ 
fering in several varieties from the European type—var. Braunii 
( 7 . Braunii , Dur.), var. muricata (. I. muricata , Dur.), and var. 
Bootti ( 7 . Boottii , A. Braun in lit.), all of them from the North¬ 
eastern States ; also 7 . Tuckermanni , A. Braun in lit., from Mas¬ 
sachusetts, and I. saccharata, Engelm., from Maryland.. 
1874. In Dr. Parry’s Botanical Observations in Western Wyo¬ 
ming, Am. Naturalist, viii. 214, 215, I gave an account of the 
three western species : 7 . Bolanderi , Engelm. ; 7 . pygmcza , En¬ 
gelm., and 7 . Nuttallii , A. Br. in lit. 
1877. My notice of 7 . melanospora , Engelm,, from Georgia 
was published in the Trans. Acad. Sci. St. Louis, iii. 395, note.. 
1878. In Coulter’s Botan. Gazette for January, p. 1, I gave 
an account of 7 . Butleri, Engelm., found in the Indian Territory 
west of Arkansas. 
§ 2 . Morphology of Isoetes. 
The species of Isoetes are the simplest vascular plants known. 
They consist of a short trunk* with root-fibres at its base and 
leaves on its top, normally withoul branching and without any 
axillary productions.f 
The trunk is generally depressed, broader than high, or 
flatter in some species ( 7 . Engelmanni) , and thicker and more 
globose 7 in others ( I. melanopoda ) , but its form is not con¬ 
stant ; it is concave on the upper side and even somewhat 
funnebshaped where the leaves are inserted, while the underside 
shows in almost all the N. American species two grooves and in 
many exotic ones three grooves, dividing the trunk more or less, 
deeply into two or into three lobes. The iiumber of lobes rarely 
varies, so that among the many hundreds and even thousands of 
American specimens which have passed through my hands, I 
have found only a single, normally bilobed, one with three lobes 
this was an 7 . riparia from Philadelphia. In the 3-lobed species 
* A very complete account of the structure of the trunk is given by H. Mohl in Linnsea 
xiv. (1840) i8r, and of the whole plant and its morphology by’A.. Braun in the Isoetes der 
f Abnormally the -Isoetes trunk has been seen divided, probably in consequence of some 
injury; I myself have seen a specimen of I. Tuckermani with four distinct bunches or 
leaves from a single trunk. K. Goebel found a proliferous Isoetes with lateral shoots in, 
place of spore cases. Bot. Zeitung, 1879, No. 1. 
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