24 BOTANICAL GAZETTE [JANUARY 
The cause for the varying behavior of the strands in the two kinds 
of spores was not determined, but the establishment of this fact sug- 
gested that any experiments on the plant which might affect nutrition 
and growth ought to have a more marked influence in determining the 
kind of spore formed if applied when the sporocarps contained Spo- 
rangia about ready to form tetrads. The various methods herem 
described were all found to give the best results if applied at this time. 
Various cultures were grown in ponds, in the open air, and in the 
greenhouse. Careful records were kept covering such points as rate 
of vegetative growth, color, and vigor of plants, length of petioles, 
length of time before the appearance of sporocarps, the nature of the 
sporocarp, the causes producing the largest and most abundant 
sporocarps, and the causes of blasting of sporocarps and of their 
complete suppression (details of these cultures will be published in 4 
later paper). 
The experimental work was begun in Chicago, June 20, 1995; 
and continued until the latter part of September; it was repeated again 
during the same period in 1906; and then carried on continuously 
from June 1907 until the present time. 
On June 20, 1905, I found Marsilia quadrijolia growing in Hull 
Court pond at all depths from 30°™ beneath the surface to 20-25°" 
above it on the banks. It was in a most luxuriant condition, some 
of the rhizomes being more than 2™ in length. There was also one 
tank of growing plants in the greenhouse. Sods from the pond were 
taken up and transferred to the greenhouse, where they were placed 
in four large tanks (60 by go°™ and 30°™ deep). These were supplied 
with soil (a rich black loam) spread evenly over the bottom to a depth 
of 1o°™, in which the sods were transplanted at one end of the tank 
and covered with water to the depth of 5°™. In a few days these 
tanks were elevated 10°" at one end. This left the soil at the upper 
end out of water, but submerged the plants, which were at the other 
end, about 10°". The tanks were then numbered 2, 3, 4, and 5; 
and placed under as great a variation of light as was possible to obtain 
in the greenhouse. All other conditions were kept as nearly uniform 
in all the tanks as possible, but on clear days there was considerable 
variation in temperature, as shown by the table of temperature 
readings. 
