1904] CURRENT LITERATURE 479 
before the appearance of uredosori. In the next stage intercellular protomy- 
celium begins to appear. The patches of mycelium are connected with the 
“nucleoli” mentioned above. These are the centers of development for the inter- 
cellular mycelium. The course of development of P. glumarum {follows the same 
lines. 
Some of the author’s figures admit of a different interpretation from that 
given. It is difficult to see how a nucleus being dissolved by a substance diffused 
throughout the cell as the mycoplasm would be can be cut away on one side in 
such an abrupt way as figured in p/.z. It would seem possible that the proto- 
plasmic connections extending from nucleoli to the intercellular protoplasm 
represent haustoria, for, to use the author’s own words, they give exactly the same 
impression as a young haustorium of the Uredineae-H. HassELBRING. 
THE REGULATION of turgor in molds is again the subject of study, this time by 
PANTANELLI,4+ working with Aspergillus. The author points out that, since in 
these organisms the cell walls are normally in a state of tension owing to the 
pressure within, the method of plasmolysis is not available directly as a measure 
of turgor pressure. Incipient plasmolysis will occur only after the application of 
an external pressure which is equal to the normal pressure of the vacuole plus that 
of the stretched wall. He further shows that the pressure which influences the 
wall is made up of at least three components: the osmotic pressure of the vacuole, 
the pressure of swelling of the protoplasm itself (Quellungskrajt, closely related, 
if not identical with the pressure of imbibition in organic bodies), and the tension 
of the surface films. The latter is exerted toward the center of the cell, and is 
negligible when compared with the other two which are exerted in the opposite 
‘direction. An ingenious method for approximating these two outwardly directed 
forces is used in the work. It is based on measurement of cell shrinkage in plas- 
molyzing solutions. To control the results obtained by plasmolysis, the method 
of determining the freezing-point of expressed sap is resorted to. 
Cells of this form live but a few days and practically all the cells of a culture 
die when spores are produced. Thus it is necessary to be sure one works with at 
least a great majority of living cells. The pressure of swelling decreases with age 
of the cell, while the osmotic pressure of the sap first rises and later falls, but is 
always dependent upon the pressure of the nutrient medium. The total turgor 
pressure of a cell depends in great measure upon conditions of nutrition, rising 
with increase of sugar in the medium, sinking with lack of oxygen. Other con- 
ditions, such as temperature changes, anaesthetics, etc., affect turgor pressure, 
and the author is convinced that in these changes we have a true response within 
the protoplasm itself. When the fungus responds to sudden increase in external 
osmotic pressure, its adjustment takes place at a rate which is related to the velocity 
of penetration into the protoplasm of the solute used. This leads to the idea that 
the perception of the osmotic stimulus occurs only when this solute has distributed 
itself throughout the protoplasm.—B. E. Livincston. 
44 PANTANELLI, E., Zur Kenntnis der Turgorregulationen bei Schimmelpilzen. 
Jahrb. Wiss. Bot. 40: 303-367. 1904. 
