138 BOTANICAL GAZETTE [February 



gases imprisoned between the floral parts under water. The writer 

 (4) has noted elsewhere that in Elodea ioensis, which has a long- 

 stalked staminate flower, a bubble of gas is generally associated 

 with the partly opened sepals, giving extra buoyancy to the sub- 

 merged flowers, which tug at their anchorage like captive balloons. 



No prolonged observations w r ere made on the possible perio- 

 dicity in the release of the staminate flowers of Vallisneria, although 

 doubtless there is a relation between their detachment and the 

 gases given off by the plant during times of brighter illumination. 

 On one occasion it was observed that as the sun came up from 

 behind a building and its direct rays fell on the spathe of the 

 staminate inflorescence the rate of detachment was considerably 

 increased for a time. In Elodea canadensis (2) there is a correla- 

 tion between the coming of strong light in the morning and the 

 rate of detachment of the staminate flowers. Svedelius reports 

 that the staminate flowers of Enalus acoroides are released mainly 

 (if not exclusively) at periods of low tide. This habit is of peculiar 

 significance from the fact that at high tide the pistillate flowers of 

 that plant are wholly submerged and pollination would be impos- 

 sible. No explanation of this relation was suggested in the paper. 



The sepals of the staminate flower of Vallisneria completely 

 invest the stamens until some time after the flower reaches the 



/ 



surface. They then slowly recurve, the smaller one being first 

 to open (pi. IX), and as it touches the w r ater it seems to function 

 in orienting the flower so that when the pair of lateral sepals open 

 there are formed 3 boatlike structures which engage the surface 

 film and float the flower. This tiny flower, with its upraised 

 stamens and pollen mass, is so snugly fitted to the surface film by 

 its 3 broad areas of contact that it is kept in equilibrium under 

 all ordinary circumstances. They are rarely overturned, even by 

 rather vigorous agitation of the water, but maintain a strict right 

 angle to the surface film. So slender an object as a needle if thrust 

 into the water among these floating flowers and slowly withdrawn 

 will be covered by the flowers that have been drawn up with the 

 film of water about the needle and may be seen standing out 

 radially from it on all sides. Once overthrown, however, they are 

 not again righted, but lie partly under water. 



