ON A MINUTE NOSTOC WITH SPORES, ETC. 373 



itself a decision is^ of course, no longer possible, since the 

 spores characteristic of Cylindrosj^ermum apparently just as 

 little come to development in the gonidial state, as do the 

 ' manubria ' of the Rivulariea?." (This last allusion has a 

 bearing on Lichina, &c., Avhich the author thinks have plants 

 appertaining to E,ivularieoe for their basis, but without 

 manubria.) I Avould venture to suggest, were such Alga3 as 

 these truly seized upon by this completely innocuous parasite — 

 which, if the hypothesis be true, rather tends to favour the 

 growth andvigour of the "gonidia" — we should hardly expect 

 that, on the other hand, the innate or inherited tendency to 

 produce " spores " would at the same time become wholly 

 extinguished. It would, I should venture to suppose, seem 

 probable, even admitting the views of Schweudener and 

 Reess as regards Nostoc, that Cylindrospermum is not likely 

 to have anything to say to the '' gonidia question." But the 

 isolated observation, for the first time herein recorded, Avould 

 seem to show that Nostoc, too, may form spores, though it be, 

 indeed, so very excei^tionally, and so extremely rarely. 



The main object, then, of the present communication is to 

 offer the following three suggestions which occur to me : — 



1. To suggest the possibility that, if we may conceive 

 Dolichospernumi, &c., excluded from the "gonidia question " 

 as forming special fruit (that is, "spores"), so might we 

 regard Nostoc as excluded, though its formation of spores be 

 so extremely rare. Seemingly, indeed, the capacity of forming 

 spores by an algal species, supposed to become occasionally 

 lichenized, is not a reason against the hypothesis as viewed by 

 Schwendener — he only assumes that such an example of the 

 alga surrenders, or leaves in abeyance, its tendency to the 

 production of s^^ores. 



2. To suggest that there are veritable lichens which live 

 submerged, and produce their apothecia. I presume, how- 

 ever, it might be replied that such may have received their 

 inoculation by the parasite during some season of drought, 

 when the alga lay " high and dry." 



3. To suggest the possibility that the spores of Collema, 

 if " sown" on some other gelatinous substratum, besides that 

 of Nostoc — say, for instance, a Palmella or Mesotsenium— 

 might equally well germinate, penetrate therein, and develop 

 a hypha. 



There seems, I venture to think, no a priori reason against 

 this latter supposition — inside the Nostoc, the "reserve- 

 stuff^' of the spore being exhausted, and the chains of 

 Nostoc filaments admittedly intact, and no " root-hairs" as 

 yet formed, the only next immediate source of nutriment for 



