1903] Robinson,— Generic Position of Echinodorus parvulus 87 
tive revision of the group, which has yet appeared, also treats Æ. par- 
vulus as a synonym of Æ. Zene//us. Curiously neither Buchenau nor 
Micheli speaks of the uniseriate carpels, originally described in 
Schultes’ Systema! and so clearly figured by Seubert in the Flora 
Brasiliensis,? although both of the later authors refer to the plate in 
question. Struck by the difference between the North American and 
the figure of the Brazilian plant I have examined all the South Ameri- 
can specimens of A/isma tenellum (Echinodorus tenellus) in the Gray 
Herbarium and find that they agree perfectly in having capitate, 
spirally arranged achenes, quite in the manner of the North American 
E. parvulus, with which, in other respects also, the South American 
plant appears specifically identical. 
The question at once presents itself whether we have here to do 
with two South American plants, one with achenes in a single ring 
and the other with achenes in a head. ‘There are many reasons, how- 
ever, for believing that this is not the case, but that not only the orig- 
inal description of Alisma tenellum but Seubert's description and 
figure are entirely in error in representing the carpels in a single ring. 
This question can only be decided by the examination of the original 
material of the species. Happily, to those of us who apply priority 
under the genus, the doubt about the true South American Alisma 
tenellum will in no way affect the standing of our own Echinodorus 
parvulus. 
Until 1895 the North American plant was uniformly referred to 
Echinodorus, but of late in the Memoirs of the Torrey Botanical 
Club, in the Illustrated Flora,* and in Professor Britton’s recently 
issued Manual,’ it is classified as an Alisma. It is natural to suppose 
that this transfer, made in direct opposition to the expressed views of 
three such authoritative writers and specialists upon the A/smaceae as 
Engelmann, Buchenau, and Micheli, would have demanded more than 
ordinary care and attention to the actual characters; and it is accord- 
ingly disappointing to find, on the contrary, that the fruit, in which, 
as we have seen, the chief generic distinctions are to be found, 
instead of being critically studied could not have received even the 
most cursory inspection by the writers making the transfer. 
As shown above, the early representation of Aisma tenellum, pub- 
1 vii. pt. 2, 1600 (1830). " *i. 85 (1896). 
? Seubert in Mart. Fl. Bras. iii. pt. 1, 105 (1847), t. 15, f. II. 
? v. 24 (1895). 5p. 54 (1901). 
