Riana. . re * - ba my 2 POOR eS} Cae ee es 
Bid dd ies RT 
1906] TRANSEAU—BOGS OF THE HURON RIVER VALLEY 29 
the fact that plants grown in bog-water cultures develop normally. 
The light conditions in the several cultures were the same, direct 
sunlight being avoided by a cloth screen. It is evident that in this 
case there is no response to strong light in the development of the 
palisade tissue (49). It would seem rather to be a response called 
forth by a reduced transpiration current (44, p. 7). As to function, 
it may aid in the transfer of food materials as suggested by HABER- 
LANDT (20, p. 260). 
Fic. ee plants showing effect of surrounding “conditions. From 
photographs. 
This plant proved to be the most plastic of all of the species used 
in the experimentation, and was the only one which showed marked 
variation in the internal structures. Ecologically the results indicate 
(t) that an undrained peat substratum may cause xerophilous struc- 
tures, but that the effect is to be correlated with lack of aeration of : 
the substratum rather than with the acidity; (2) that the same effect 
may be induced by lowering the substratum temperature (the air 
temperature remaining the same), and thus impeding the rate of 
