FOLIAGE-LEAVES AND THE CHLOROPHYLL FUNCTION. 527 
of Cucurbita Pepo, Ricinus communis, Zea Mays, and Phaseolus 
multiflorus, and tips of branches of adult specimens of Cardio- 
spermum Halicacabum, Dolichodeira tubiflora, and Helianthus 
annuus. The seedlings were placed partly or entirely in the 
apparatus necessary to exclude CO,, and the tips of the branches 
were securely sealed-in while attached to the plant. All the plants 
named were found capable of carrying on growth and develop- 
ment of the leaves, under the conditions named, during periods 
of from 6 to 8 days. No distinct statement was made as to how 
nearly the leaves attained a normal or adult size, but in some of 
the plants named a much longer period is necessary. This point 
has received especial attention from Vóchting. By a series of 
tests with tips of shoots and branches of Mimosa pudica, Solanum 
tuberosum, Tropeolum Lobbianum, and Cardiospermum Hali- 
cacabum, he found that none of these plants were able to form 
perfect leaves in an air free from CO,. In some instances 
forms not widely divergent from the normal were attained, 
and these began to show signs of deterioration if the experiment 
were prolonged to cover from 14 to 18 days. The contradictory 
results of Vines and Véchting are doubtless to be attributed to 
the difference in the duration of the experiments in each instance. 
Vöchting found that the development of a leaf from the rudimen- 
tary condition to the unfolding of the lamina proceeds in a 
normal manner in an atmosphere free from CO,, and is therefore 
at the expense of food stored in the axis or seed. Batalin (1) 
had previously concluded that the development of a seedling is 
at the cost of the stored food in the seed until the supply is 
exhausted; but Vóchting found that when the unfolding of the 
lamine began, both in the seedling and in shoots, abnormal 
features appeared and deterioration soon set in. For example, 
such an occurrence was noted in Solanum, although the tubers 
several centimetres distant were richly loaded with starch. 
Vóchting accounts for such results by the supposition that the 
conducting tissues in the later stages of development of the leaf 
are adapted for the conveyance of food-material, downward and 
away from the lamina, and that movement in the opposite 
direction is effected with difficulty ; and since a limited growth 
may be accomplished with the small amount thus conveyed to 
the lamina, but deterioration soon occurs, he concludes that the 
growth and normal continuance of leaves is in some manner 
connected with the assimilation processes. 252 
Pa 
