n8 THE WATERLILIES. 



therefore believed the flow to be due to a higher pressure in the plant than 

 outside. He agreed with Lechartier in believing that there is a move- 

 ment of gases in the air-canals of Nymphaeaceae toward the leaf, to make 

 exit through the stomata, and concluded that stomata in general are for 

 the exit rather than for the entrance of gases. Goebel's (1893) experi- 

 ment seems to differ from these. On a dull autumn day petioles of 

 N. rubra and stellata (?) were cut off under mercury near the water surface 

 and held as nearly as possible erect. The smaller intercellular spaces 

 became in every case injected with mercury up to the lamina, even in 

 pieces 60 cm. long. This would indicate a considerable negative pressure. 

 Recognizing the positive pressure as noticed by Sachs (though without 

 mention of Lechartier or Barthelemy), Goebel concludes that when the 

 amount of assimilation is slight there is a rarefaction of air in the canals 

 caused by the continuance of respiration ; but when assimilation is active, 

 part of the oxygen is given off into the intercellular spaces, and reaches 

 the air-canals and finally extends to the rhizome and root. This view at 

 once harmonizes the observed phenomena and explains the presence of 

 the air-canals. It is the more plausible when we consider the peaty soil 

 in which our waterlilies grow and the general absence of free oxygen in 

 submerged muddy material. 



Since the behavior of the flowers has for its object the successful 

 reproduction of the species, and since there is in this connection a very 

 distinct series of movements and activities, the whole relation of these 

 parts has been reserved to this point, although there would be good reason 

 to take them up under the head of irritability. The rise of the flower bud 

 from the rhizome to the surface of the water takes place in the same man- 

 ner as that of the leaf, and the peduncle must be regulated in length by 

 the same stimuli that regulate the petiole ; it is even capable, in Castalia, 

 of a slight elongation if the water level rises after the flower first comes 

 into bloom. A peculiar adaptation occurs, on the other hand, in plants of 

 any species, when grown in very shallow water, say 10 to 15 cm. This 

 often occurs in our gardens, where we have the tropical kinds as near to 

 the surface as possible in order to keep them warm. Now, the flower bud 

 is first pushed out from the apex of the plant in a very immature state, 

 and it is to finish its development as it is rising through the water. In 

 very shallow water, therefore, it reaches the surface when it is by no means 

 ready to be exposed to the air. The situation is recognized at once by 

 the plant, and the peduncle bends to one side and becomes S-shaped 



