1908] BRIEFER ARTICLES 53 
This table shows that suitable material can easily be obtained in winter 
for the demonstration of protoplasmic streaming. Of the plants studied, I 
should recommend Nitella and Elodea as good examples of rotation; 
Gloxinia speciosa, Tradescantia zebrina and virginica, Abution striatum 
(hyb.), Lycopersicum esculentum, W hitlavia grandiflora, Cucurbita maxima, 
Lobelia Erinus, and Saxifraga cotyledon palmata for circulation. Gloxinia 
Speciosa is especially good, as the entire hair cell can be brought within 
the range of vision, and a constant change observed in the arrangement 
of the strands, circulation passing into rotation as the temperature rises. 
Campanula, Lobelia, Vinca, Streptosolen, Capsella, and Ampelopsis have 
markings on the cell wall which obscure the view of the protoplasm to 
some extent. 
A complete study of the streaming involves the measurement of its rate 
at Various temperatures from minimum through optimum to maximum. 
Results of such study, expressed in a graph, are available for Chara, Elodea, 
and Vallisneria in DaveNport’s Experimental mor phology (12226), and for a 
common Nitella in GANONG’s Laboratory course in plant physiology (p. 19). 
My own graph for Tradescantia shows a curve much flatter than that 
above mentioned for N itella, though otherwise somewhat similar to it— 
Grace L. BUSHEE, Smith College, N orthampton, Mass. 
ON PLASMOLYSIS 
According to the conception of plasmolysis developed by DE VRIES and 
EFFER, the contents of a cell contract and round up when it is placed in a 
ution whose osmotic pressure exceeds that of the cell sap. This is 
explained by supposing the outer layers of protoplasm to be impermeable 
to the substances in solution which produce the osmotic pressure. If the 
Protoplasm is permeable to these substances, either wholly or in part, 
deviations from the rule given above will occur. Deviations have in 
fact been described by several authors and explained by supposing the 
Protoplasm to be more or less permeable to the substances in solution, 
which enter the cell sap and increase its osmotic pressure. : 
I Propose in this paper to describe deviations which range from those 
which are very slight to those which are of extraordinary intensity, the 
ee of whose nature is entirely different from the one mentioned 
ve. 
Pr 
sol 
. My attention was first called to these deviations some three years ago 
y the results of some of my experiments on the réle of osmotic pressure* 
TA bri : ae ed ; ‘ 
23227, an . lee of these investigations appeared in oo coge — ot. 
