590 
Journal of Agricultural Research 
Vol. XXVIII, No. 6 
also been produced from single ascospores from apple, and other hosts. No 
suggestions are made as to the taxonomic status of these fungi, other than that 
they are closely related and that some of them have previously been referred to 
as forms of Melanops quercuum. 
In 1919 Putterill ( 6 ) described a canker of apple trees in South Africa which was 
caused by a fungus closely resembling Botryosphaeria ribis. This fungus even 
possessed the chromogenesis ( 6 , p. 264) described by Grossenbacher and Duggar 
for the currant parasite. The characters used by Putterill to distinguish his 
fungus, for which he proposes the name Botryosphaeria mali , are a difference 
in the width of the asci and in the size of the stromata. Recently Stevens and 
Jenkins (13) have demonstrated that the currant cane blight fungus occurs on 
horsechestnut, and certain varieties of rose, and that it is parasitic on the rose, 
causing cankers on the stem and sometimes killing whole canes. 
LIFE HISTORY STUDIES 
Culture Methods. —During the last two years the writers have had under 
observation over three thousand cultures of fungi belonging to this group, more 
than ninety per cent of which have fruited. In view of the difficulty experienced 
by some investigators in obtaining pycnospores of these fungi in pure cultures, 
a brief statement of the methods used may be of interest. It is certainly true 
that these fungi fruit but rarely in the arid and often superheated environment 
furnished by many laboratories. If, however, the cultures are kept in an ordi¬ 
nary greenhouse the temperature of which varies through a range from 50° to 
70° F. or more, they will fruit abundantly on many agar media, on sterile twigs, 
and on cornmeal in flasks. Summer temperatures in the vicinity of Washington, 
D. C., are apparently too high to permit these fungi to fruit readily but good 
results have been obtained during the summer in unheated wooden buildings at 
Wareham and Woods Hole, Mass. 
Our cultures were first transferred to the greenhouse in an endeavor to secure 
more variable temperatures, as a result of the observations of Stevens (12), re¬ 
cently emphasized by Harvey (3), that the temperature of bark out of doors 
often fluctuates with great rapidity. There is as yet, however, no certainty 
that the abundant fruiting is due to temperature range or fluctuation alone. It 
may as well be due to the greater humidity, or to a combination of temperature 
and humidity, or to some as yet unrecognized and incidental factor. It is suf¬ 
ficient for the purpose of the present investigation to be able to secure abundant 
pycnospore production with reasonable certainty in pure cultures made either 
from mycelial transfers or from ascospores or pycnospores. 
Results. —In the course of this culture work the writers have verified the life 
histories recorded above many times. Within the last two years alone pycnidia 
of the Dothiorella type have matured in pure culture from one hundred eighty 
single ascospores from currant and from seventy-seven single ascospores from 
apple. Mature pycnidia of the Sphaeropsis type have been produced in pure 
culture from ninety-five single ascospores from apple. 
The name Dothiorella is here used to include such pycnidial forms as are 
congeneric with the macro-pycnidial stage of Botryosphaeria ribis and appar¬ 
ently also Dothiorella gregaria Sacc. Typical material is found in specimens 
3407, 3408, and 3409, Fungi Columbiani. This is not Dothiorella ribis (Fuck.) 
Sacc. Number 3407 labeled “Macrophoma type” is a mere form of Dothiorella 
growing on young shoots and producing smaller and simpler pycnidia. The 
name Macrophoma has been most frequently applied to immature forms of 
Diplodia and Sphaeropsis, in which the spores are colorless. The name Sphaer¬ 
opsis is here used to include pycnidial forms congeneric with the form usually 
called S. malorum on apple and whose ascogenous stage is Physalospora. 
