268 FUNGOUS DISEASES OF PLANTS 



the epidermis, and between the epidermis and cuticle. In these 

 situations it spreads slowly. According to some writers the prin- 

 cipal development at first is immediately beneath the cuticle. 

 That is particularly true, according to reported observations, on 

 the leaves. On the fruit, however, both the cuticle and the epi- 

 dermis are soon broken and disappear as the spot becomes scabby 

 in appearance. Upon the pear I have quite generally found the 

 mycelium to be subepidermal at the edge of the scabby spots. It 

 may form a layer several times as thick as the diameter of the hyphae, 

 and as the epidermis wears off, this mycelial layer is exposed, and 

 beneath this the cells of the host may become corky, as shown 

 in Fig. 119. The mycelium is olivaceous or sometimes reddish- 

 brown in color, closely septate, sinuous and irregular in branching. 



FIG. 120. GERMINATING SPORES OF FUSICLADIUM 



The olivaceous growth on the surfaces of the fruits, leaves, and 

 twigs is, however, made up very largely of the short, erect conidio- 

 phores. These conidiophores arise from the subcuticular or sub- 

 epidermal mycelium, break the cuticle if the latter is still intact, 

 and a spore is soon developed at the tip of each. A spore may 

 be borne when the conidiophore has attained a length of four or 

 five times its diameter. However, when this spore is abscised, 

 the conidiophore grows further, leaving a slight knee or other 

 evidence indicating the point where the previous spore was borne. 

 In this manner many successive conidia may be produced, and 

 the conidiophore therefore becomes flexuous and irregular. It 

 may also become septate in time. The conidia on both hosts 

 measure ordinarily 28-30 x /-QA 6 - They are more or less ovate 

 in form, the basal end being more truncate. They are ordinarily 

 continuous but may become once septate with age. The color is 

 fuliginous or olivaceous, sometimes having a slight reddish tint. 



