224 
METHODS IN PLANT HISTOLOGY 
culture may be employed, as described in the chapter on temporary 
mounts (chap. v). The uredospores germinate readily all summer, 
but in most forms teleutospores will germinate only in the spring 
following their maturity. However, the teleutospores of “lepto” 
species, like Puccinia xanthii on Xanthium, canadense (cocklebur), 
will germinate as soon as they ripen, and will serve equally well for 
study. If a particularly good specimen 
is secured, it may be preserved by the 
method previously described for desmids, 
except that in this case it might be worth 
while to attempt staining with Mayer’s 
haem-alum or with eosin. 
Gymnosporangium, which is rather 
common on Juniperus virginiana (red 
cedar), forms its basidia in the “cedar- 
apple” stage. Bring the cedar apples into 
the laboratory in late winter or early spring 
and put some into a dish of water. The 
yellowish, gelatinous strands with the 
germinating teleutospores may appear 
within 24 hours. The various stages are 
easily recognized under a low-power dry 
lens without even crushing the gelatinous 
masses. Fix in 10 per cent formalin for 
24 to 48 hours. The material may be left 
here indefinitely. In chromo-acetic acid 
the gelatinous substance goes to pieces. 
Stain in iron-alum haematoxylin and 
follow the Venetian turpentine method; 
or, when the thick glycerin is reached, 
mount in glycerin jelly. The material 
spreads out better and fewer basidia are torn off from the teleutospores 
in glycerin jelly than in the Venetian turpentine. 
The interesting nuclear conditions in the life-history of a rust 
which has uredospores, teleutospores, and aecidiospores are not diffi¬ 
cult to demonstrate. After the uredospore or teleutospore stage has 
been fixed in chromo-acetic acid and washed in water for an hour, 
treat with 10 per cent hydrofluoric acid in water for an hour and then 
continue the washing in water for 24 hours. If fixed in alcoholic 
Fig. 61 .—Aecidium on Hepatica: 
fixed in chromo-acetic acid with a 
little osmic acid, and stained in safra- 
nin, gentian-violet, orange; from a 
preparation by Dr. Wanda Pfeiffer 
Vestal. X950. 
