132 



BOTANY. 



The walls are thinner and not so dark in color, and they are 



covered with minute spines. They have also short stalks, but 



•e^gj^ these fall away very easily. These one- 



MSwIiSl^ celled spores of the red-rust form are 



called ' ' uredospores. ' ' The uredospores 



and teleutospores are sometimes found in 



the same pustule. 



It was once supposed that these two 

 kinds of spores belonged to different plants, 

 but now it is known that the one-celled form, 

 the uredospores, is a form developed earlier 



in the season 

 than the teleu- 

 tospores. 



223. Cluster- 

 cup form on 

 the barberry. 

 — On the bar- 

 berry is found 

 still another 

 of the 



Fig. no. 

 Barberry leaf with two 

 diseased spots, natural 

 size. 



Figures 153-135. 



Fig. in. 

 Single spot 

 showing cluster 

 cups enlarged. 



split margin 

 -Cluster-cup stage of "wheat rust. 



Two cluster form 

 cups more en- 

 larged, showing w heat rust, the 



sniit marcrin. 



' cluster cup ' ' 

 stage. The 

 pustules on the under side of the barberry leaf are cup-shaped 

 the cups being partly sunk in the tissue of the leaf, while 

 the rim is more or less curved backward against the leaf, and 

 split at several places. These cups occur in clusters on the 

 affected spots of the barberry leaf as shown in fig. 1 1 1. Within 

 the cups numbers of one-celled spores (orange in color, called 

 aecidiospores) are borne in chains from short branches of the 

 mycelium, which fill the base of the cup. In fact the wall of 

 the cup (peridium) is formed of similar rows of cells, which, 

 instead of separating into spores, remain united to form a wall. 

 These cups are usually borne on the under side of the leaf. 



