214 FUNGOUS DISEASES OF PLANTS 



of certain scale insects. In Florida it commonly succeeds attacks 

 by the white fly, or Aleyrodes. It is, however, in other localities 

 equally as abundant following other species of aphid-like insects. 

 The fungus has long been a nuisance in the Mediterranean 

 orange groves, and for some years has been of sufficient abun- 

 dance in both Florida and California to require control measures. 



The fungus. The mycelium of the fungus consists of large 

 branched threads which are at first olive green and velvety, be- 

 coming with age deep brown with a tendency to scale or break 

 up into small patches. The hyphae are closely septate, often con- 

 sisting of chain-like groups of cells, readily separated one from 

 another. Moreover, abundant branching and cementing together 

 of these branches may give rise to a kind of false stratum or 

 tissue ; anastomosing also occurs. Careful microscopic examina- 

 tion has failed to disclose any penetration of the host by this 

 organism, and it would appear that it utilizes as a source of 

 nutriment only the so-called honeydew resulting from the pres- 

 ence of the insects referred to. Certain modified, knob-like 

 branches of the hypha; are commonly found, but it is apparent 

 that these liyphopodia serve merely as organs of attachment. 



The propagative stages of this fungus are numerous. Conidia 

 of several types, stylospores in pustules, pycnidia, and perithecia 

 may be present. The conidia may be simple cells abscised from 

 upright hyphse or they may be more highly differentiated compound 

 structures. The stylospores are produced from small conidiophores, 

 developed within peculiar, elongate, flask-shaped structures. These 

 form a conspicuous part of the fungus and are present throughout 

 a considerable period of its growth. They are particularly evident 

 when branched or variously subdivided, or adherent in groups. 

 The pycnidia are relatively minute, but they occur in considerable 

 number distributed over the entire surface. The spherical perithecia 

 are somewhat larger than the pycnidia and, like those of other 

 members of this family, are closed bodies which disseminate their 

 spores only upon disintegration. The perithecium may contain 

 several short, stout asci with eight dark, elliptical, three-to-four 

 septate spores. With the diverse sorts of spore forms mentioned, 

 it will be evident that the fungus is rapidly distributed, and conse- 

 quently spreads with alarming facility under favorable conditions. 



