a A STUDY OF THE PROBLEM OF WATER ABSORPTION. 33 
normal condition, then, either the integrity of that membrane 
is not lost when it is broken or a new membrane is formed 
about the protoplasm very soon after the old one is destroyed. 
The spherical masses within the plasmolysed cells show them- 
selves capable of taking up water, even when the solution is 
diluted immediately after plasmolysis. It is hard to think 
that the short period of time necessary to dilute the plas- 
: molysing solution is sufficient to allow of much differentiation 
2 in the outer layers of the protoplasm. If we dispense with 
ee. the idea that a new membrane is formed immediately after 
ee the old one is disrupted, then the only conclusion to which 
we can come is that the membrane surrounding the normal 
protoplast, if such a membrane exists, is not very susceptible 
to mechanical injury. One would expect to find a living 
membrane more delicate than non-living membranes, yet we 
do not know of an inert membrane through which solid bodies 
may be forced without rendering it quite permeable. 
2. The Concentration of Cell-Sap. 
Along with the assumption that a semi-permeable mem- 
brane surrounds the living plant cell, goes the further 
assumption that the solution contained within the membrane 
is as concentrated if not more concentrated than the liquids 
surrounding the turgid cell. If this were not true the cell 
would not remain turgid, but would lose some of its water and 
become plasmolysed. If, therefore, cell-sap be obtained from 
cells that are as nearly alike as possible it should represent the 
‘ concentration of the solution originally within the cells. If 
i; cells like those used in this experiment be placed in the sap, 
ae they should remain practically normal as regards their turgor. 
But if this sap solution be concentrated it should then plas- 
i molyse these cells. In order to determine whether or not this 
re would take place, the following experiment was performed: 
Monilia sitophila (Mont.) Sacc. was grown on pieces of 
potato that had been washed in running tap water for forty- 
eight hours. From these cultures fifty-two and one-half 
grams of spores were collected. They were obtained by in- 
verting the cultures and shaking them above a piece of paper. 
TE oe ae 
