seedlings from which the seeds had been removed, and which were 
growing in water culture (fig. 3). In this last case the laterals were 
very long. It seems probable that in each of these instances we have 
to deal with a problem of nutrition, but how cutting off the supply | 
of stored food can cause the tip to branch, as it does when the growth _ 
is checked, is not evident. 7 | 
32 BOTANICAL GAZETTE [yoLy 
FOOD. . 
The possible effect of the quantity of food in the seed upon the~ 
development of the zone of hairs in water has been mentioned. — 
SCHWARZ (75, p. 162) found that if the food were taken away (how 
he does not state) or used by acceleration of growth by heat, the hair 
production ceases sooner than usual, the length of the zone depending 
the food is exhausted and the plants die. In the case of the plants 
which form the zone, the cessation of hair production may be due te 
the hydrostatic pressure of the water; to lack of mineral salts, oxygen, 
or transpiration; or to the stimulating effect of the water upon growt. 
of the root. Hydrostatic. pressure can hardly be the cause when corn — 
roots produced hair continuously in dilute solution of presumably 
the same pressure as tap water. 
OXYGEN. 
Although much has’ been written upon the relations of air and 
oxygen to growth, here as elsewhere little has been done upon root 
hairs. The statements of V6cHTING, PERSECKE, and SCHWARZ seem 
