362 BOTANICAL GAZETTE [APRIL 
cases they are prostrate. The species found are paper birch (Betula 
papyrifera alaskana), peat bog birch, late alder (Alnus sinuata), and 
net-veined willow (Salix reticulata). 
Toxicity of the substratum is evidently a large factor in the stunting 
of trees in sphagnum, although several other factors are partly respon- 
sible—GrorcE B. Rice, University of Washington, Seattle, Wash. 
PROTHALLIA OF LYCOPODIUM IN AMERICA 
Recently I described in this journal (63: 66-76. 1917) the prothallia 
of 5 species of Lycopodium found near Marquette, Michigan. In that 
article (p. 71) I mentioned the difficulty in distinguishing between the 
prothallia of L. complanatum and those of L. obscurum, and a footnote 
was inserted to attempt to clear up a doubtful situation. In the paper, 
fig. 13 isnamed L. obscurum, but in the light of what follows it is evidently 
L. complanatum. 
On May 27, 1917, I found several prothallia which suggested that I 
had not correctly identified those of L. obscurum. Upon following up 
this suggestion, on August 29 I found a small patch of sporelings of this 
species, and secured some 30 gametophytes with and without sporelings. 
They are of the L. annotinum type and not of the L. complanatum type, 
as stated in my paper. The excuse for the error is that hitherto the 
prothallia of L. obscurum were unknown; those of L. complanatum do 
not all grow in the same position, nor are they alike in size and color; 
and finally, the young sporelings of the two species are very similar. 
An illustrated account of the sporeling and gametophyte of L. 
obscurum will be given in a later paper—EarLe AuGuSsTUS SPESSARD, 
Marquette, Mich. 
