FOLIAGE-LEAVES AND THE CHLOROPHYLL FUNCTION. 541 
Lsopyrum and! Ozalis are capable of forming perfect leaves which 
are capable of continued normal existence, inferentially, until the 
supply of plastic material becomes insufficient. Leaves attained 
full size and continued a normal existence on ZEsculus in Coren- 
winder's tests, on Fagus in those of Jost’s, and on Hibiscus and 
Justicia in my own. 
Furthermore, it is shown that the behaviour of leaves in an 
atmosphere free from CO, and in darkness exhibits the greatest 
divergences. Thus the leaves of Mimosa and Phaseolus may 
attain normal size in darkness, but quickly perish in an air free 
from CO, Exactly the reverse relations prevail in Jsopyrum and 
Oxalis. The accompanying alterations in the growth of etio- 
lated plants still further warrant my assumption that the 
behaviour of such plants cannot be held to be analogous to that 
of specimens grown in an air free from CO,, and that in the 
former many other forces are operative in the production of the 
“rigour of darkness ” besides those concerned in food-formation. 
Since the growth of a plant in an atmosphere free from CO, 
practically suspends the food-forming processes, I have deemed 
it of the greatest importance to analyze the relations existing 
between the growth of such organs and the supply and conduction 
of food from storage organs or from other members. 
A special series of tests was made by myself with Zea with 
reference to this point, and it was found that marked reaetions 
might be seen after 10 days. The control plants exhibited a 
more vigorous growth, and on the 12th to 14th day deterioration 
began in the leaves grown without CO, (see Plate XIX. fig. 5). 
The reserve food was not exhausted in the seeds of either the 
enclosed or control plants. This result leads to the conclusion 
that seedlings may not develop normally beyond a certain 
point at the expense of stored food in the seed, contrary to the 
views of Batalin (1) The rapidly increasing needs of a seedling 
are usually partially met by substances formed in the young 
leaves after a certain stage of development has been reached. 
If, on the attainment of this stage of development, it is still 
compelled to depend on the supply from the seed, deterioration 
willsoon ensue. While the growth of the leaf, or rather its 
consumption of plastie material may be represented by a 
logarithmie eurve during the period of rapid expansion, the 
amount of food which may be conveyed to it may be represented 
The cross section of the conducting 
by an algebraie curve. 
y g 2o 
LINN, JOURN.— BOTANY, VOL. XXXI. 
