262 I TNGOUS DISEASES OF PLANTS 



The fungus. The life history of the fungus has been con- 

 siderably studied, and it is probable that some spore stages which 

 have been described are not at any rate common stages in the 

 life cycle. In general, two spore-producing stages may be found, 

 the conidial and the ascigerous stages. The conidial stage has 

 been described as Ramularia Titlasnci. This appears in early 

 summer, as a rule, or so soon as the pale centers of the spots 

 have been developed. Small, tuberculate stromatic masses are 

 produced upon the mycelium beneath the epidermis, and from 

 these arise a small group of simple hyphse, which rupture the 



FIG. 114. LEAF SPOT OF STRAWBERRY 



epidermis and produce conidia which may become one or several 

 times septate. The conidia, according to Dudley, measure 20- 

 40 x 3-5 ft (Fig. 115, a). 



The ascigerous stage is not so commonly found and is in no 

 case developed until late summer. A membranous perithecium, 

 characteristic of this family, is then produced within the leaf, al- 

 though at maturity a considerable part of the perithecium may be 

 exposed. Relatively few asci are developed, the asci containing 

 invariably eight hyaline, uniseptate spores with acute tips (F'ig. 115). 

 It would appear that the spores are not ordinarily mature until 

 late winter, or at least not ejected until that time. Moreover, 



