178 
METHODS IN PLANT HISTOLOGY 
the bottle or dish. If the paraffin sticks, as it probably will, break 
the dish and cut the paraffin into suitable blocks. Or, the paraffin 
may be poured into the usual imbedding dish, keeping it just warm 
enough to let the organisms settle; then cool and cut into blocks. 
Safranin, gentian-violet, orange, are very good for olden stages, 
especially for pyrenoids and starch. Iron-alum haematoxylin is 
better for nuclei and the younger stages of oogonia, antheridia, and 
new colonies. 
Fig. 36.— Volvox: surface view of several cells, fixed in the hot aqueous corrosive sublimate- 
acetic acid mixture, stained in iron-alum haematoxylin, and mounted in Venetian turpentine; B, 
fixed in chromo-acetic acid, but otherwise treated like A; C-G fixed in 1 per cent chromo-acetic 
acid imbedded in paraffin and cut 5 ju; C, E, and F stained in iron-alum haematoxylin; D, and G 
stained in safranin gentian-violet orange; C, new colony showing pyrenoids, p, and nucleus, n; 
D, a nearly mature antheridium; E, young egg; F, egg before fertilization; G, egg after fertilization, 
showing oil globules, o; pyrenoids, p; starch cut off from pyrenoid, s. All X780. 
Figure 37 shows that even such delicate forms as Volvox can be 
imbedded in paraffin without shrinking. 
The Power’s Methods.—-Professor J. H. Power’s mounts of 
Volvox and other members of the Volvocaceae have been the delight 
and despair of both botanists and zoologists for many years. They 
have never been surpassed and, probably, never equaled. Professor 
Powers has kindly given me an outline of his methods; but, as in 
other phases of technic, judgment, skill, and patience must be fur¬ 
nished by the student. 
