172 
METHODS IN PLANT HISTOLOGY 
the forms are small, like Anabaena, smear a slide lightly with Mayer’s 
albumen fixative, as if for paraffin sections, add a drop of the material 
and allow it to dry over night or for 24 hours; then immerse the slide 
in strong alcohol for a few minutes, and then proceed with the 
staining. Cyanin and erythrosin form a good combination for differ¬ 
entiating the granules. Delafield’s haematoxylin, used alone, stains 
some granules purple and others red. Iron-alum haematoxylin 
is excellent for heterocysts. With patience, these Wasserbliithe 
forms may be stained in iron-haematoxylin and brought into Venetian 
turpentine, from which they will yield much better preparations 
than can be secured by the drying- 
down method. 
Sometimes Anabaena, mixed 
with Gloeothece or Gloeocapsa, occur 
floating in gelatinous masses which 
hold together fairly well, so that 
it is easy to fix in the chromo- 
acetic-osmic solution recommended 
for Oscillatoria, stain in iron-alum 
haematoxylin, and follow the Ve¬ 
netian turpentine method. 
With such material we have 
tried a more expeditious method 
with excellent results. After staining in haematoxylin, we have 
used a series of alcohols, 2J, 5, 10, 15, 20, 30, 40, 50, 70, 85, 95, 
and 100 per cent, allowing only 3 or 4 hours for the entire series. 
Then use mixtures of clove oil and absolute alcohol, beginning 
with 1 part clove oil to 4 parts alcohol, followed by equal parts 
clove oil and alcohol, then 3 parts clove oil to 1 of alcohol. At 
this point, stain in orange dissolved in clove oil. Drain off the 
stain and transfer to pure clove oil. Then place the material in 
thin balsam, about 1 part of the balsam used for mounting to 3 parts 
of xylol. Here the material may be kept indefinitely. Mounts 
may be made in balsam from this stock. Figure 35 was drawn from 
material prepared in this way. 
Fig. 35.— Anabaena: A, hormogonium 
showing well-defined nuclei; B, older filament 
showing a spore and a heterocyst. 
