98 Rhodora [JUNE 
collection. In nearly all cases there is a single specimen of the spe- 
cies in a central position and alone on the slide so that it may be 
easily found. These are referred to by number, e. g. Н. C. no. 701, 
etc. Reference is occasionally made to the slides of the Johnson 
collection now the property of the Cryptogamic Department of Har- 
vard University. These are referred to as H. J. no. 650, ete. АП 
localities from which specimens have been actually examined by the 
writer are followed by an exclamation point. In other cases the 
author's name in parentheses follows the record. Enough of the 
synonymy is given under each species to refer to the original place of 
publication and to published figures. Measurements are from New 
England specimens only, unless otherwise stated. А key is given 
which will help in the identification of the species. 
MICRASTERIAS Agardh, 1827. 
Cells usually large, commonly sub-circular or elliptical in outline, 
deeply constricted; semicells usually five lobed, occasionally three 
lobed, much compressed; polar lobe broadening distally, frequently 
with a median notch at the middle of the outer border; lateral lobes 
usually dichotomously divided; zygospores globose, with stout spines; 
surface often ornamented, usually with acute granules. 
A Key ro THE New ENGLAND SPECIES OF MICRASTERIAS. 
A. Polar lobe entire or slightly retuse, lateral lobes of semicells two, trans- 
versely placed, generally entire and attenuated to their extremities. 
1. Polar lobe fusiform, end strongly convex. 
1. Polar lobe narrower and smaller than the basal lobes. 1. М. oscitans. 
2. Polar lobe nearly as wide as basal lobes and of similar size. 
2. M. laticeps. 
II. Polar lobe spreading, usually with a retuse end. 
1. Apices of polar lobe bifid, narrower than basal lobes. 
3. M. pinnatifida. 
2. * 4 4. 4 acute, nearly as wideas “ © 
4. M.arcuata. 
B. Lateral lobes of semicells four, radiately disposed and broadest distally. 
I. Polar lobe entire, lateral lobes barely divided. 5. M.depauperata. 
П. 4 ©“ with a median incision. 
1. Lateral lobes generally much divided, interlobular incisions narrow. 
a. Inter-lobular incisions not deep. 
(1) Depth of polar lobe much less than half the length of the semicell. 
(a) Cell nearly as broad as long, smooth. 6. M.truncata. 
(b) * much longer than broad, surface granular. 
. M. Jenneri. 
(2) Depth of polar lobe at least half the length of the semicell. 
8. M.conjerta. 
b. Interlobular incisions deep. 
