28 BOTANICAL GAZETTE [JANUARY 
results. By this time I had discovered that the megaspores were the 
first to succumb when the plants were chilled, and I also found an 
occasional sporocarp, among those which had not apparently been 
blasted, which showed that the megasporangia and oldest set of micro- 
sporangia had been killed, but the younger microsporangia were in a 
healthy state (fig. 13, b,c). So far as I could determine, these sporo- 
carps were ina fair way to reach maturity, notwithstanding the fact 
that the megaspores were all dead. I then shortened the time of 
application of the spray, in order to determine the shortest period 
which would kill the megaspores and yet not blast the entire sporocarp. 
This I found to be no easy task, as it is not possible to determine 
exactly, from external appearance, the stage of development of the 
sporogenous tissue. I was able finally to be reasonably sure from 
GREENHOUSE TANKS AND WATER PIPES 
IN THE SUNLIGHT 
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Diagram of piping and position of tanks in greenhouse 
their size and thickness when sporocarps had reached the mother cell 
stage. In such sporocarps, under the conditions of this experiment, 
the application of the cold spray day and night for 48-6o hours would 
not cause the entire sporocarp to damp off, but most of the sporocarps 
when sectioned showed only traces of megaspores in the sporangium. 
It was in these sporocarps that I got such a great variety of forms of 
microspores (jigs. 15-22). 
The sporocarps treated less than 48 hours generally developed 
normally, while those treated for a longer period than 60 hours gen- 
erally damped off. I was able to treat plants in August and Septem- 
ber 1907, in the south end of the greenhouse, in stronger light and at a 
higher temperature (see table) for a much longer time (76-96 hours) 
before blasting occurred. Also in the same year I was able to grow 
abundant and normal sporocarps in tanks out of doors, at tempera- 
tures shown in the table, in as much as 20°™ of water. At the same 
