24 • OBSERVATIONS ON COLLEMA. 



knows no Alga? which could be transformed by the influence of a 

 fungus into Usnea, Cladonia, Cetraria, etc., but that it appears to 

 him that the parasitism has been rendered by de Bary and Reess 

 extremely probable for the ' Collemacea}.' " 



Schwendener himself, in his later memoir,* figures certain 

 Nostoc specimens whose gelatinous matrix is seen to be penetrated 

 by what he denominates fungal threads (Pilsfaser), and these he 

 points to as evidence of the truth of his view ; that is, that they 

 become the hypha, and that the phenomena of growth thereby 

 induced absolutely convert the " Nostoc " into " Collema ;" and he 

 firmly holds his figures prove the case. Now, Reess, referring to 

 these very figures, conceives the fungal threads depicted must be 

 strictly those of a (destructive) fungus — a mould, in point of fact ; 

 he thinks, indeed, they may be anything whatever, but one thing 

 clearly he avers, be they what they may, they are by no means a 

 Collema-hypha, founding his opinion, of course, upon the know- 

 ledge gained from his recently conducted experiments. So that 

 whatever may be the opinion of other observers as to the result of 

 the researches of Reess, at least the examples adduced by 

 Schwendener relating to Collema, it would appear, must be held as 

 inconclusive. 



It may, perhaps, be not inoj)portune to observe that, as must be 

 well known, the gelatinous masses of those Alga3 which grow on wet 

 rocks and-such situations, be they Palmellaceous or Chroococcaceous, i 

 are prone to be more or less permeated by " mycelioid " threads, 

 and even some such as would fairly well accord with those Reess 

 depicts for Collema, though not so copiously branched, may not 

 be unusual. Some of these threads are, at least occasionally, those 

 of indubitable (devastating) fungi, which, when they " attack " 

 certain cells, destroy them ; other threads, doubtless quite distinct, 

 can apparently live independently and innocuously, though probably 

 drawing nutriment from the common mucous matrix. What a 

 monstrous and abnormal " Lichen-th alius " thus not unfrequently 

 comes to view — a variable " hypha " interruptedly running hither 

 and thither, and accompanied by " gonidia " of very heterogeneous 

 character ! The plant named by Kutziiig, Trichodictyon rupestre, 

 which can hardly be doubted to be the same as Cylindrocystis crassa, 

 de Bary, is frequently (though not always) accompanied by a 

 number of fine filaments (which seem, however, to be inarticulate), 

 twisted in and out through the gelatinous mass made by the alga, 

 but so running as to leave rounded spaces between containing the 

 groups of the Cylindrocystis-cells ; they seem, in fact, to urge their 

 way between the more dense mucous envelopes formed round the 

 groups of dividing cells, simply because they find the intervals, 

 being softer, more readily permeable. These filaments, whatever 

 their nature really may be, cannot be doubted I should think to be 

 foreign, though they were actually introduced into the generic 



* " Die Algeiitypen," etc., pp. 28, 29, t. II., ff. 13-15. 



