90 OTIS F. CURTIS AND REGINALD H. COLLEY 
(5), or by running through the grades of xylol into a weak solution of 
balsam in xylol, which was then allowed to thicken gradually to the 
right consistency for mounting. The stain keeps well in both media:' 
Shrinkage and distortion, especially in young cells, is practically 
negligible when reasonable care is used in handling material. For ■ 
class use the Cyanophyceae, Nemalion, and forms without large vacu- 
oles can be mounted directly in balsam from clove oil or xylol with little 
or no shrinkage. Forms with large vacuoles may show some dis- 
tortion when transferred from absolute alcohol to clove oil or xylol 
but the amount of shrinkage may be decreased by making the change 
more gradually. Apparently there is no need of carefully timed 
treatment as theie is rarely any dangei of injury or overstain; for, with 
most material, the results vary little whether the time of fixing and 
staining be twelve hours or three days. A few forms, particularly some 
of the red algae, should rarely be left in the solution more than twelve 
hours as they soften very quickly ; other forms, although they may seem 
to have been softened and spoiled are hardened and restored to normal 
appearance in the higher alcohols. Pfitzer suggests the use of ammonia 
to take out the excess stain, but it has been found sufficient in most 
cases to rinse in water or simply to lengthen the time in the lower 
alcohols. 
. Experiments were conducted to determine the value of the com- 
bination killing and staining solution on widely separated genera of 
the algae, including Oscillatoria, Lyngbya, Volvox, Spirogyra,Zygnema, 
Oedogonium, Ulva, Enteromorpha, Nitella, Ectocarpus, Sphacelaria, 
Fucus, Nemalion, Callithamnion, Ceramium and Polysiphonia, and 
on various Diatoms, several genera of the Agaricaceae, and young root 
tips. The stain proved very satisfactory for the algae, with the 
exception of Ceramium and Polysiphonia, and the Diatoms, but further 
work must be done with fungi and higher plant tissues before definite 
conclusions can be stated. 
The value of the method may be indicated by a brief statement of 
the general results on some of the forms studied: In Oscillatoria and 
Lyngbya the chromatin granules are brought out distinctly because 
they stain more deeply than the rest of the cell contents. In Entero- 
morpha the nucleus is clearly differentiated; the pyrenoid is stained 
faintly and appears to stand in a colorless area, the chromatophore, 
which is haidly stained at all. In Sphacelaria the young propagulae 
show practically no shrinkage, even when material is removed from 
