SOME MELIOLICOLOUS PARASITES AND COMMENSALS 
FROM PORTO RICO 
FF, L. STEVENS 
(WITH PLATES V AND VI AND FIVE FIGURES) 
The genus Meliola is distinctly tropical and within the tropics 
is most abundant in humid locations, although there are many 
species found in arid regions. It is chiefly in the warm humid 
locations that the species are accompanied and overgrown by other 
fungi; frequently so heavily overgrown as to entirely obscure the 
Meliola itself, stop spore production, and even the presence of the 
Meliola may be proved only by very careful search. The exact 
relation which these fungi bear to the Meliola is not known. ‘True 
parasitism, owing to the dark color of the mycelium, is much more 
difficult to demonstrate than in the case of Cicinnobolus on the 
Erysiphaceae, so familiar in temperate climates. It is extremely 
probable that all of the forms except the last considered are para- 
sitic. ‘This last is probably merely an accidental associate. Some 
of the pycnidial forms were formerly regarded as belonging to the 
Meliola cycle, but more recent studies do not support this view. 
Two of the hyphomycete genera have been regarded by some stu- 
dents of Meliola as the conidia of Meliola, while others treat them 
as independent fungi, and still others evade the question. 
It is not possible to regard the ascigerous forms of Microthyrium, 
Dimerium, Podosporium, Calonectria, etc., as genetically connected 
with the Meliola, nor is there any more reason for assuming genetic 
connection in the case of any of the forms mentioned later. They 
may be merely commensals favored by the environment, but there 
is very strong circumstantial evidence that they are parasitic, and 
there is no sufficient reason to regard any of them as belonging to 
Meliola. The special statement in this connection relating to . 
Arthrobotryum and Helminthosporium is given later. The speci- 
mens upon which this article is based are filed under the Meliola 
host, and are deposited as indicated in an article by Miss YouNG.* 
* Youne, E., Mycologia 7:143. 1915. 
227] {Botanical Gazette, vol. 65 . 
