1893.) Proceedings of Section G, A. A. A.S. 341 
25. ELIZABETH G. BRITTON: A revision of the genus Phys- 
_ wnitrivm.—Physcomitrium pyriforme of the Manual is not 
_ DP. pyriforme of Europe, but is P. turbinatum, which proves to 
our most widely diffused species. An interesting new 
species is also described from California under the name P. 
- pherotheca. Instead of six species in the United States, there 
ae probably nearly double that number. Florida forms of 
this genus are probably referable to three distinct species. 
_ Mr. Barnes thought the separation of P. turbinatum from 
P. pyriforme well taken. 
: 26. W. T. SWINGLE: Cephalurus mycotdea and Phyllosi- 
phon sp., two parasitic alge new to North America.—The lat- 
ter of these alge was gathered in the Dells of the Wisconsin 
fer, three days before (Aug. 19th), and heretofore known 
oly from a few places in Europe. It forms pale spots upon 
the leaves of Arisema, and is probably widely distributed. 
The alga is a genuine parasite, living within the tissues of the 
at The Suggestion is made that this habit may explain one 
yin which fungi have been derived from algz without hav- 
| rere through aquatic forms. The first alga mentioned 
; : tag upon Magnolia, and has been found in this coun- 
fore by lichenologists, but not reported. 
; TUESDAY AFTERNOON, AUGUST 22. 
- tales V. COVILLE: An analysis of the condt- 
 tnditions ae the distribution of plants.—The environmental 
t i hi % plants, when reduced to their lowest terms, are 
wnt Water, food, air and mechanique. 
thought it would be well to include evolu- 
Portant part played by fire in determining 
Mr. Coville explained that this was not classt- 
_condition, but was put under heat. He 
€nsion, as used by MacMillan, was included 
ue. 
© Arruur: Deviation in development due to the use 
-—It was shown that immature seeds bring 
ive over the vegetative parts, causing a com- 
er fruitage. It was pointed out that such 
tly great 
