4 .KCIDI \ 



The oldest spores being a1 the top, bhey separate as soon .-is 

 mature, and arc blown away by the wind; fresh spores are 

 produced for a time from below. Since these cups are in dense 

 clusters over the whole of the affected spot, they are known as 

 ■•Cluster-cups." The mycelium in the leaf continues to develop, 

 and the spot enlarges and ceases to be round. But the swelling 

 of' the tissues within which the mycelium is living can be 

 carried to such an extern as to distort and curl the leaf, much 

 in the same way that /'J.mascus deformans (the Peach Leaf-curl) 

 affects the Peach leaves. The epidermis above and around the 

 spot, also, often becomes coloured red or purple by an anthocyan- 

 derivative, both these effects being a response by the leaf-cells 

 to the stimulus of the parasitic growth, and perhaps part of an 

 effort to throw off or checkmate the invader. The mycelium, 

 moreover, is not confined to the leaves ; it may originate in 

 the petiole, in the stipules and in the stem. In the latter case 

 it causes notable curvature and distortion ; an instance is 

 recorded where the curved gall-like mass, formed on the stem, 

 measured as much as 10 cm. in length, and similar but smaller 

 growths may frequently be met with. 



Here should be noticed the close parallelism, up to a certain 

 point, in the formation of the spermogones and the secidia — 

 they have similar shapes, they are both enclosed by a layer of 

 sterile hyphae, they arise in ( usually) quick succession on the 

 Mime mycelium, they give off basipetal chains of spores from 

 their base. On the other hand, besides the difference in the 

 nuclei, the secidiospores differ from the spermatia in their larger 

 size, in possessing a large store of reserve food, in their capacity 

 for germination, and for producing infection in another plant. 



The .Ecidiospores. 



The mode in which the secidiospores are produced is as 

 follows : — The upper cell of the sporiferous hypha usually 

 divides into two, an upper sterile cell, and a lower fertile or 

 basal cell, each with one nucleus. The upper cell disintegrates 

 and perishes; the lower fertile cells conjugate with one another 

 in pairs, the process consisting in the formation of a small hole 



