FUNGI 
223 
stage on barberry belongs in the life-history. The aecidium on bar¬ 
berry cuts easily in paraffin (Fig. 60). If the aecidium stage is not 
easily available, there are various aecidia which are just as good, or 
even better, for morphological study. The aecidia growing on 
Euphorbia maculata (spotted spurge) are abundant and are very easy 
to fix and cut. The infected plants are also very easily recognized, 
normal plants having the prostrate habit, while infected plants 
become erect and the internodes become greatly elongated. Aecidia 
growing on Arisaema triphyllum (Jack-in-the-puplit) are also easy 
Fig. 60 . —Puccinia graminis: photomicrograph of aecidium stage on barberry. Fixed in 
chromo-acetic acid and stained in cyanin and erythrosin: Eastman Commercial Ortho film, Wratten 
E filter (orange); arc light; Spencer 16-mm. objective N.A. .25; Bausch and Lomb projection 
eyepiece; exposure, £ second. X47. Negative by Dr. P. J. Sedgwick. 
to cut. The Aecidium on Hepatica has large nuclei and affords 
particularly good views of the intercalary cells. 
The special chromo-acetic-osmic-acid solution is recommended 
for fixing and iron-haematoxylin with a faint touch of orange is a 
satisfactory stain (Fig. 61). 
It is rather difficult to get good sections of uredospores and teleu- 
tospores of Puccinia graminis , because the leaves of wheat and oats 
are refractory objects to cut (Fig. 62). For illustrative purposes, 
soak the leaves, scrape off the spores, and study without sectioning. 
For sections, select species growing on less refractory hosts. 
Everyone who studies the rusts should attempt to germinate the 
uredospores and teleutospores. For this purpose the hanging-drop 
