194 THE FUNGI WHICH CAUSE PLANT DISEASE 



the mycelium. Fumago camelliae Catt. is a conidial form of this 

 species. 



M. penzigi Sacc."^"^ is found on Citrus forming a sooty black 

 mold. It subsists on "honey dew," folloAving principally certain 

 insects as Aleyrodes, Ceraplastes, Dactylopius, and Aphis. The 

 species is quite similar to the preceding. 



The hyphae are from olive-green to dark brown and when old 

 are connected into a compact membrane. The fungus is entirely 

 superficial, possessing, however, small knob-like projections for 

 attachment and large discs (hyphopodia). Reproduction is by 

 conidia, pycnidia, stylospores and perithecia. 



Webber says: 



"Several forms of conidia are produced, some being but slight 

 modifications of the common cells of the mycelium, while others 

 are compound spores. Pycnidia are small, spherical black repro- 

 ductive bodies, about 40 ij, in diameter, and are usually present 

 in considerable numbers in the mycelium. They may be readily 

 seen with a strong magnifying hand lens, but cannot be definitely 

 distinguished from perithecia or the young stages of the stylospores. 

 Stylospores are borne in conceptacles, which in their simplest form 

 resemble flasks with long drawn-out necks. Frequently, however, 

 they are much branched, and as they project from 1 to 2 mm. be- 

 yond the mycelium they form quite a conspicuous part of the 

 fungus. They are easily recognized with the unaided eye, and can 

 be seen with considerable distinctness with a hand lens. Perithecia 

 are black, spherical reproductive bodies closely resembling pycnidia, 

 from which they can not be distinguished with a hand lens. How- 

 ever, they are larger, being eighty micro millimeters in diameter. 

 Each perithecium contains several asci and each of these bears 

 eight ascospores. Some of the investigators who have studied 

 this disease have failed to find perithecia, and only twice has the 

 writer found them in his examination of material from Florida. 



The various reproductive bodies other than perithecia, partic- 

 ularly the conidia and stylospores, are developed in great abun- 

 dance." 



M. niessleanea Wint. is common on Rhododendron. 



Several entomogenous fungi i"-"» have been found which by prey- 

 ing upon those insects which secrete honey dew, lessen the injury 



