8 Brannon . — The Structure and Development of 
While direct sunlight appears necessary for the continued 
growth of the plant, it cannot endure strong light when only 
slightly submerged. If after collection the plants are placed 
in water in a shallow vessel, exposed to the direct rays of the 
sun, their normal colour rapidly changes to a brownish yellow, 
and they give every evidence of rapid decay, evidently due to 
the effect of direct sunlight and the accompanying rise of 
temperature. Direct experiments were not made to deter- 
mine the sensitiveness of Grinnellia to changes of temperature 
alone, but incidentally it was observed that a sudden variation 
of io° to 1 5° C. from normal (temperature of if C. in the 
water of Vineyard Sound) for any length of time is destructive 
to the tissue. Fishermen reported collections of this plant in 
the winter. Having cut through the ice they could scrape 
it from the piles, in water of which the temperature was 
probably not lower than 2° to f C., while in the summer the 
temperature of these waters, as previously stated, is 15 0 to 
17 0 C. 
The three types of fronds, antheridial, carposporic, and 
tetrasporic, show a similar degree of sensitiveness to direct 
light and sudden rise of temperature, but can be preserved in 
a normal condition for several days in the laboratory if 
properly shaded, if the normal temperature of the containing 
water be maintained, and if the sea-water be changed every 
thirty-six to forty-eight hours. 
Nowhere are the effects produced by the change of light 
and temperature more perfectly shown than in the process of 
sporing and germination. The spores are liberated in great 
numbers during the night, particularly the second night after 
the plants are collected. However, numerous experiments 
proved that this process occurs in some degree during the 
day, differing in this respect from the sporing methods 
observed in some other Florideae, notably Champia parvula. 
Immediately after collection, the carposporic and tetra- 
sporic plants were separated in order to study the germination 
of their respective spores. It was found that the carpospores 
are usually closely grouped in great numbers immediately 
