Considered in Relation to its Function . 413 
permeable membrane, though if this is the case in the living cell, it is 
difficult to see how the sugar formed by the chloroplast is passed out into 
the surrounding cytoplasm. 
On the other hand, the absorption of water may be due to imbibition 
by the internal colourless stroma. One would expect neither of these 
processes to take place after treatment with chloroform. 
It has been suggested that this split is really the normal process of 
division in the chloroplast. It may certainly be an analogous process, but 
its rare occurrence, except under certain conditions, points to its having 
been artificially induced in these experiments by definite changes of 
environment. 
Normal division of the chloroplast may be due to similar osmotic 
differences existing between cytoplasm and chloroplast, but the appearances 
noted in our experiments, certainly cannot be explained by the assumption 
that a greater number of chloroplasts were caught in the act of dividing, 
in one case than in the other. 
Summary. 
By microscopic investigation of living and fixed material, we have 
come to the conclusion that in the large chloroplasts of Chlorophytum datum , 
Selaginella Martensii , and S'. Kraussiatia , the chlorophyll is restricted 
to the peripheral ring of the chloroplast, where it is held in the meshes 
of a network. 
This is in agreement with the views of Timiriazeff concerning the 
function of chlorophyll in absorbing the radiant energy necessary for the 
photolytic decomposition of carbon dioxide. 
Our confirmation of the observations of Nageli and Timiriazeff in 
regard to the splitting of the chloroplasts when placed in a solution of small 
osmotic strength, is also in agreement with this view of their structure. 
