Ig01] SPORANG/A AND GAMETOPHYTES OF SELAGINELLA 135 
strobilus are fertilized, the formation of new sporangia is checked. 
The sporophylls begin to decay, as finally does the axis imme- 
diately below the fruiting head. The production of new strobili 
went on until late in August, at which time all the strobili were 
shed, whether fertilized or not. In September vigorous vegeta- 
tive growth took place during the fall rains, and continued until 
checked by several days of very cold weather in December. In 
the latter part of the same month, upon removing the snow that 
covered the plants to a depth of six inches, they were found to 
be green and ready to grow at any favorable moment. Large 
sods were lifted, without disturbing the plants, and brought into 
the warmth of the greenhouse, whereupon they responded 
promptly to the blander conditions. After a week, upon gently 
disentangling the individuals in order not to detach the semi- 
decayed strobili which were partially covered by the soil, I 
found several young sporophytes which had thrust their cotyle- 
dons and roots through the crevices of the megasporangia. 
From this it seems safe to assume that an embryo may have two 
periods of growth separated by one of quiescence, quite com- 
parable to those of seed plants. 
SELAGINELLA RUPESTRIS. 
There could be hardly a more striking contrast in the exter- 
nal appearance of two closely related plants than exists between 
these two species of Selaginella that are natives of New England. 
S. rupestris is to be found in the most exposed situations, grow- 
ing on the granite rocks on the mountain sides, wherever there 
has been enough weathering to insure the deposition of a little 
soil in the hollows. For six months of the year they endure 
alternate drought and drenching, and the frequent and rapid 
changes of temperature which are characteristic of this region, 
with no more protection than is afforded by their own structural 
adaptations. The midsummer conditions are even more trying. 
The plants that were studied for this work grew on bare rocks 
upon which the sun beats nearly all day from June to September. 
The fruiting spikes are to be found in profusion at all times of 
