[Vor. 7 
292 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
In the case of the Canada field peas the seed were germinated 
on paraffined wire mesh over tap water, and growth was per- 
mitted to proceed in diffuse light until the plumules were well 
established with unfolding green leaves. Solution cultures were 
then made in the usual way as especially described in an earlier 
paper (Duggar, '19). All cultures were therefore arranged in 
duplicate in tumblers holding about 250 cc., and the seedlings 
were inserted through holes in paraffined paper covers (peas), 
or through notches in the corks (corn). Seedlings of uniform 
size were selected and all cultures were placed in the green- 
house, freely and equally exposed to sunlight. A mineral nutri- 
ent solution, designated in the paper referred to above as solu- 
tion B, was employed. It should be observed that this solution 
contains not merely all essential ions, including NO,, but con- 
tains these in favorable proportions and concentrations for the 
promotion of excellent growth. 'The date of the beginning of 
the experiment was taken as that on which the cultures were 
exposed in the greenhouse. At intervals of a day or more apart, 
the cotyledons of successive pairs of cultures were cut away 
so as to determine their influence on growth, and the time of 
exeision of the last pair represented the practical exhaustion 
of these food reserves. In the case of corn the young plantlet 
with attached scutellum was carefully dissected out from the 
endosperm, an operation which may be effected with very little 
diffieulty after germination begins. In all other respects the 
eorn eultures were treated in precisely the same manner as the 
peas. "The total green weights of all cultures are given in table r, 
and the appearance of the peas at the end of the period of obser- 
vation, 24 days, is shown by pl. 7. 
From the results with peas it is clear that for a growth interval 
of 24 days the removal of the cotyledons after the second day 
induces a marked depression in the growth rate, and this de- 
pression is increasingly less, until, when the removal of the 
cotyledons occurs after 7 days, the amount of growth is very 
nearly the same as in the control, with cotyledons intact. Du- 
plieation of this experiment with some modifications in the 
interval led to the conviction that under the conditions the 
cotyledons are practically exhausted in somewhat less than 10 
days. It might be pointed out that the removal of the coty- 
