Ill] THE WATER-SHIELD 29 



not freeze, the submerged leaves may vegetate throughout the 

 winter. In 191 1, the present writer observed a number of 

 plants of the Yellow Waterlily flowering without having pro- 

 duced any but submerged leaves. Possibly this was associated 

 with the peculiarly brilliant sunshine of that summer, which may 

 have supplied the submerged leaves with unwontedly intense 

 light for assimilatory purposes. 



Castalia alba produces submerged leaves less freely than 

 Nymphaea lutea and they are said to be incapable of surviving 

 the winter; the first leaves of the seedling are of this type 

 (Fig. 13)- 



Fig. 14. Cahomha aquatica. Habit drawing to show entire floating leaves and 

 dissected submerged leaves. [Goebel, K. (1891-1893).! 



The American Water-shield, Cahomba^ which is placed in a 

 different tribe from Castalia and Nymphaea^ and might, indeed, 

 almost be assigned to a different family, produces submerged 

 leaves of a very distinct type^ (Fig. 14). They are finely dissected 

 and comparable with the submerged leaves of various Batrachian 

 Ranunculi. 



1 Goebel, K. ( 1 89 i-i 893) and Raciborski, M. (i 8942). 



