an ne 
260 FOUNDATIONS OF BOTANY 
red rust. A little later the black spores appear, produced from the 
same mycelium.« This growth is chiefly upon the stems and sheaths. 
Fic. 191. — Spore-Formation in Potato-Blight (Phytophthora infestans). 
A, a well-developed group of stalks, proceeding from a mass of mycelium inside 
the leaf and escaping through a stoma; B, a young, unbranched stalk. h, 
hyphe of mycelium ; 0, stoma; s, spore. (Both figures greatly magnified, B 
more than A.) 
311. Cluster-Cup Stage. — Note with the naked eye and with a 
magnifying glass the appearance of the cluster-cups upon the bar- 
berry leaf. Fresh specimens should be used, if available. Note 
whether the leaf is changed in form or color in any part occupied 
by the fungus. Note the number of cups in a cluster, the position 
on the leaf (which surface ?), the form and size, especially the height. 
