PEACH SCAB AND ITS COISTTEOL. 



13 



Fig. 5. — Cladosporium carpophilum: a, Con- 

 idiophores and conidia from fruit lesions; 

 6, conldiophores and conidia from twig 

 lesions; c, conidiophore from leaf lesion; 

 d, and e, fragments of mycelium from 

 Lima-bean agar culture, showing develop- 

 ment ofehlamydospores. Camera-lueida 

 drawing. (Magnified 485 times.) 



the more exposed cells thicken and darken and the individual cells may 

 assume the characters of chlamydospores (fig, 5, d and e). On old cul- 

 tures on steamed peach twigs or certain agar preparations, small, irreg- 

 ularly rounded to distinctly elongated, olivaceous, sclerotioid masses, 

 usually less than one-third of a milli- 

 meter in diameter, may be found. The 

 outer cells of these bodies are thick 

 walled and olivaceous and frequently 

 bear conidiophores. The inner cells are 

 thin walled and colorless, with an 

 abmidant content of oily material. 



Conidiopliores. — T h e conidiophores 

 (fig. 5, a, h, and c) are short, erect, 

 more or less flexuous, one to several 

 septate, rarely branched, ohvaceous 

 hyphse, distinctly enlarged at the base 

 and often tapering irregularly toward 

 the apex. Their dimensions vary with conditions, though in nature 

 they are fairly uniform during the early stages of sporulation. The 

 conidia are produced acrogenously, beginning usually when the spo- 

 rophores are about 30 to 35 n long. The conidiophores elongate 

 apically as conidia are developed, the places of attachment of de- 

 tached spores being marked ordinarily by small wartUke processes 

 or by geniculations on the sporophores. The extent of this type of 

 elongation, which is quite variable, determines the ultimate length of 

 the conidiophores. On the overwintered twig lesions the conidiophores 

 borne from the subcuticular stromateoid fungal masses occur typically 

 in tufts (fig. 4), and tend to be somewhat shorter and thicker than 

 those occurring elsewhere in nature. On the fruit they grow much 

 longer, often attaining a length of 90 to 100 //. On leaf infections 

 and twig lesions of the current year they tend to be somewhat more 

 erect and less flexuous than on fruit or overwintered twigs. In cul- 

 ture there is much greater variation, the sporophores ranging from 

 undifferentiated hyphse to abnormally long, slender filaments. Meas- 

 urements of conidiophores are summarized in Table II. 



Table II.^ — Measurements of conidiophores of Cladosporium carpophilum. 



Source. 



Number 

 measured. 



Average measure- 

 ments (microns). 



Source. 



Number 

 measured. 



Average measure- 

 ments (microns). 



Length. 



Breadth 

 at middle. 



Length. 



Breadth 

 at middle. 



Fruit 



10 

 10 

 10 

 20 

 10 



63.5 

 65.0 

 73.0 

 42.1 

 42.7 



4.6 

 4.2 

 4.2 

 5.5 

 5.0 



Twig of current 



10 

 10 

 10 

 10 



48.5 

 57.9 

 60.8 

 57.0 





Do 



4.7 



Do 



Leaf 



4.6 



verwintered twig . 

 Do 



Do 



4.6 



Do. 



4.6 









1 Conidiophores in early stage of sporulation; consequently, relatively short. 



