PROGRESS OF MICROSCOPICAL SCIENCE. 
145 
Observations on Collema. — These observations are continued by 
Mr. W. Archer in c Grevillea ’ for August. The author concludes a 
paper of some length with the following three suggestions : — 1. To 
suggest the possibility that, if we may conceive Dolichospermum, &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 
formation of spores by an algal species, supposed to become occa- 
sionally lichenizecl , 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 
spores. 2. To suggest that there are veritable lichens which live 
submerged, and produce their apothecia. I presume, however, 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 Mesotfenium — might equally well 
germinate, penetrate therein, and develop a hypha. There seems, I 
venture to think, no a priori reason against this supposition — inside 
the Nostoc, the “ reserve-stuff” of the spore being exhausted, and the 
chains of Nostoc filaments admittedly intact, the only next immediate 
source of nutriment for the growing hypha would, I imagine, in the 
experiment of Reess, appear to have been the “ Nostoc-jelly.” Now a 
“ Palmella-jelly,” or a “ Mesotaenium-jelly ” (both aerial, that is, not 
under water), would seem in themselves to be possibly just as likely 
to afford the requisite pabulum for the germinating and growing 
Collema-spore. If this conjecture should be borne out, which I 
would indeed put with all diffidence, what would be the result of 
Reess’ s experiments, or, rather, what proven thereby ? Such a com- 
bination (if capable) with a Palmella or a Mesotfenium would not be 
“ Collema,” because it would not have “ nostochaceous ” gonidia, nor 
the characteristic periderm. If, indeed, we might for a moment 
assume that which direct experiment alone could prove, and a germi- 
nation of spores and penetration of the hypha of Collema with a 
Mesotfenium effected, such a “ lichen-thallus ” would be, I apprehend, 
unprecedented — a hypha like other lichen-hvplne, no doubt (but 
known to be that of a Collema), with large elliptical or cylindrical 
“ gonidia” containing a central “chlorophyll-plate,” and which would 
probably (in free nature at least) go on and produce zygospores ! 
