152 
appear in sori in which no uredospores are formed. Mount some teliospores 
in potassium hydroxide and stupy :-— 
32. Their form, size and structure as compared with uredospores; 
color, where located, in walls or contents? 
33. The thick walls and densely granular oily contents. 
34. The light spot in the center of each cell; not always evident. 
The nuclei are located here. These spores are at first binucleate but at, or 
just before germination the nuclei fuse and sexual fertilization, begun by 
the association of nuclei in the aecium, is now completed. 
The structure of the telium and its relation to the host-tissue does not 
differ materially from that of the uredinium. DRaw several teliospores 
to show structure and variations in form and size observed. 
Saprogenesis. With the ripening or death of the host, teliospores 
have been formed usually in great abundance on the straw. .When the 
grain is harvested, many teliospores are left on the stubble. Those on 
the straw go with it into the stack, then into the manure pile and finally 
with the manure back on the land. Under the conditions of moisture 
and temperati:re that starts the barberry into growth in the spring, the 
teliospores on the old straw become active. They germinate in situ form- 
ing a promycelium from each cell of the spore. Four basidiospores are 
produced from each basidium. Each is uninucleate, its nucleus having 
been derived through the reduction division of the fusion nucleus of the 
teliospore. These sporidia, as we have seen, constitute the primary inocu- 
lum which affects the young leaves of the barberry. They cannot, so far 
as is known, affect any of the cereals or grasses. 
REPORT 
1. Prepare a diagram showing the spore-forms and activities 
of Puccinia gramums Pers. in their proper sequence through the primary 
and secondary cycles. 
2. Explain the effect of the black stem-rust on the tissues of its 
host, and point out how it causes reduction in yield. 
