132 REPORT—1874., 
“parasite ” invading the various alge in question, in accordance with the new view, 
then the parasites attacking each must be mutually quite distinct species, and, taken 
on the whole, marvellously choice in their selection of ‘ host.” 
Proceeding on the latter assumption, two of the forms now brought forward 
would have to be regarded as two “new species,” falling either under the genus 
Ephebella, Itzigsohn, or Gontonema, Nylander. The three other forms would pro- 
bably have to be referred as ‘‘new species” to Spilonema, or one of them, wanting 
paraphyses, to Lichenospheria, Bornet. 
For the new view much that has been advanced by its supporters is very cogent 
and striking, if not yet conclusive. 
But in “lichens” like Ephebella, Gonionema, Ephebe, Spilonema, Lichenospheria, 
in which it is the “alga” which builds up the outward configuration of the thallus, 
and which simply harbours latent within it the parasite, the latter making itself 
externally evident only by its exserted apothecia, does it not seem inconsistent to 
describe the characters of the thallus of the alga as part and parcel of those of the 
“lichen?” Thus Bornet, in giving the characters of Lichenospheria Lenormandi, 
describes it generically thus :—“ Thallus tenellus, ramosus, fruticulosus, fere omnino 
stigonematoideus, basi corticatus ;” and specifically he speaks of it as “ Thallus fusco- 
niger, tomentoso-intricatus.” This, for so far going on the Schwendenerian view, 
is nothing more nor less than describing the characters of “ Sirosiphon divaricatus, 
Kiitz.” (the plant invaded by the “ parasite”); but when he goes on to describe the 
apothecia, the paraphyses, the spermogonia, the spores, he is giving the characters 
of the parasite and the real ‘‘ new species.” 
There can be little doubt but that amongst these Seytonematous and Sirosiphona- 
ceous Algz quite truly distinct forms occur, but that, on the other hand, there can 
be almost as little doubt but that Kiitzing has very greatly overrated their number. 
Now it is hard to conceive that one and the same parasite would care very much 
which of forms so closely resembling it invaded in order to pursue its course of life. 
Sirosiphon divaricatus seems not to differ much from S. alpinus (one of those now 
brought forward with apothecia) : now what very perceptible barrier is there to the 
supposition that the parasite which invades the former to form Lichenospheria 
Lenormandi, Bornet, might not at another time invade the latter? Would it then 
fructify in the same way, show spores alike, &c.? But the “ parasite” which does 
really invade the latter (as shown by this paper) is not the same. Are these Scyto- 
nemicolous and Sirosiphonicolous parasites, then, so extremely choice ? 
Again, two very closely allied forms of Scytonema now brought forward likewise 
showed very distinct parasites, as evinced by their spores, whilst those of one of 
them much resembled that of Strosiphon pulvinatus, an alga in itself sufficiently 
unlike the other. 
In objection to the new theory, though it has much to say for itself, in the mean 
time and whilst it is, as it were, on its trial, it might be asked at what period of the 
life of the Scytonema or Strosiphon does it become invaded by the parasite? at 
what part of the thallus does it make an entry? It must be near the base, or at all 
events not very high up, for the hypha is found growing pretty nearly pari passu 
with the growth of a branch of the alga and in the same general direction. But 
why might not the hypha grow in the opposite direction? Might it not sometimes 
enter near the apex and grow backward? Might we not sometimes expect to find 
hyphe sticking out from broken-up or distorted examples of these alge, and thus 
revealing themselves (without the whole mass being boiled in potash) whilst on 
their way to other examples of quite the same alga? Or must the hypha apper- 
taining to a particular plant have had its commencement from a spore which found 
its way to, and alighted somewhere externally upon, the particular Scytonema or 
Strosiphon ? 
An experimental decision of the “gonidia-question,” so far as it relates to these 
Se eer apie: and Sirosiphonaceous forms, is surrounded by not a few practical 
difficulties. A “sowing” of spores upon the alge (as Reiss did for Nostoc) in a 
natural condition could only be carried out by an observer residing in or close to 
the subalpine situations where these plants dwell, as they could not be cultivated 
elsewhere. In order to obtain the spores he would further have, most probably, a 
troublesome preliminary search, and, on the other hand, there would hardly be a 
