82 



PARASITISM OR POLYMORPHISM— WHICH? 



By W. Phillips. 



The little that is known of the life-history of the black moulds 

 (^Dematice), and the consequent value of any fact bearing on the 

 subject, however apparently insignificant, induces me to bring before 

 your readers a curious growth t!iat has recently come under my 

 notice. On the stump of a decayed tree was growing a dark 

 velvety fungus, covering a space of some inches, which, on re- 

 moving a portion and placing it under the microscope, was seen to 

 consist of a small forest of upright black stems, varying in length 

 from 'OOOin. to 'lin., most of them bearing sphajrical or pear- 

 shaped heads. There were at least three different species, inter- 

 mixed and associated in such a manner as to suggest the question 

 at the head of this note. The undergrowth (pi. 53, fig. 10 a a) con- 

 sisted of nearly black unbranched threads, articulated at frequent 

 intervals ; when seen by transmitted light, opaque at the base, 

 translucent towards the summit, as commonly seen in Helmintho- 

 sporia (fig. 11). When young some of these threads were sur- 

 mounted by a spha^rical head (fig. 11a), which wasa simple, thick- 

 walled cell, containing a groumous, subtransparent protoplasm, 

 which becomes at a later period dark brown, nearly opaque (fig. 

 lie), in which state it might safely be referred to 3Jonotospoi-a 

 sphcerocephala, B. & Br. Other threads were surmounted by oval 

 heads passing throusfh a similar change of density according to 

 age (fig, 11 b, d), as the sphajrical ones. These might be referred 

 to Jlonotospora rnegalospora, B. & Br. A third lot of threads had 

 heads differing from both those described, a^^proaching a pear in 

 shajDe (fig. 11 e), the dark brown contents being divided into three 

 or four portions by broad septa. These may be referred to 

 Helminthosporinm ohovatum, Berk. Now the question arises, are 

 we to consider these three forms as distinct species, accidentally 

 growing together, or one and the same species passing through 

 these several forn)s ? If we had found cither growing alone there 

 could have been little hesitation in naming it as above, but the idea 

 is forced on us that when they are found thus intermixed, they may 

 be different developments of the same species, the progression of 

 which may be best seen by the arrangement (fig. 12 a, b, c, d, e), of 

 the different heads according to age, taking the small transparent 

 sphan'ical head :is the youngest, and the septate pear-shaped head as 

 the most mature, the other forms being intermediate. .4 fact tending 

 to strengthen this view is that nearly all the heads which had 

 fallen on the matrix were the pyreform septate ones (fig. 12 e). 



In addiuon to what I have just described as the under- 

 growth, there were also seen thinly scattered taller stems, with 

 sjDhferical heads of a totally different st)'ucture (fig. 13), answering 

 to Stilbum rigidum, P. The stem consisted of a densely com- 



