26 BOTANICAL GAZETTE [JANUARY 
It fruits sparingly under water, and at a depth of 10°™ very few sporo- 
carps appear. I observed that most of these blast when about half 
grown. 
In my greenhouse cultures in 1905 I found that all the first sporo- 
carps that appeared in tank r blasted when about half grown, except 
two that happened to be about 8°™ higher than the others, due to the 
uneven surface of the soil in the tank (fig. 12,m). After the rhizome 
passed over this elevation and again sank into 8-10°™ of water, the 
‘sporocarps began to blast as before. In order to be sure that this was 
not accidental, on July 5 I lowered the water in this tank until it was 
not more than 1°™ in depth; and then nearly all the sporocarps 
matured. On July 11 I raised the water to the original level, and by 
July 16 many of the oldest of the newly formed sporocarps were 
blasting. On July 21 I again lowered the water to 1°” in depth, and 
by July 25 the oldest of the sporocarps, formed after that date, had 
safely passed the period where blasting had occurred. I then put 
on 20°™ of water and found that the blasting occurred after the sporo- 
carp had been visible only about two days, instead of four to six days 
as observed at the 10°™ level. I imbedded and sectioned many of s 
these sporocarps in order to determine the relative vitality of mega- 
spores and microspores. It was from a study of these that I conceived 
the idea of blasting the megaspores and continuing the development 
of the sporocarps containing only the surviving microspores. I shall 
speak later of the methods employed. 
I was at a loss to know just what had caused the blasting. While 
mere depth of water seemed to be the immediate cause, several factors 
were involved, such as oxygen supply, intensity of light, and tempera- 
ture, all of which were varied with the change in depth. On August 
5 I moved this tank, which had been in subdued light, to the east side 
of the greenhouse into strong light, and threw a mist of tap water over 
the plants in order to keep them saturated, but at the same time 
aerated. This water was siphoned off constantly, so that most of 
the sporocarps were at the surface. In a few days (August 11) I 
noted that blasting was occurring quite as universally as before. 
While the plants now had more light and a better oxygen supply than 
before, I had lowered the temperature during the middle of the day 
about 8° and at night about 3°. It was plain that this variation in the 
