36 WILLIAM ARCHER. 
were, on its trial, at what period of the life of the Scytonema 
or Sirosiphon does it become invaded by the parasite? At 
what part of the thallus does it make its entry? It must be 
near the base or at least 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 what is to prevent the hypha growing in the opposite 
direction? Might it not sometimes enter near the apex and 
grow backwards? Might we not sometimes expect to find 
hyphe sticking out from broken-up or distorted examples of 
these algee, and then revealing themselves (without the whole 
mass being boiled in potash) whilst on their way to invade 
other examples of quite the same alga? Or must the hypha 
appertaining toa particular plant have had its commencement 
from a spore which found its way to and alighted somewhere 
externally upon the particular Scytonema or Stirosiphon? 
The account given by Itzigsohn of Ephedella! is incomplete; 
he met with apothecia in his species of ‘‘ Scytonema,” con- 
taining asci, but they had not as yet developed spores. ‘The 
plant he had in view may certainly be said to be quite 
distinct from Scytonema myochrous. It is probable the 
fructification would also have been seen, if fully mature, to 
have been also specifically different. So too are my two 
forms, both in thallus and fructification. These, proceeding 
on the new theory, would perhaps be relegated as “ new 
lichens ” to Epheéella, Itzigsohn, or to Gonionema, Nylander ; 
but neither is indentical with Gonionema velutinum, Nyl. (of 
which I have seen examples in the late Admiral Jones’s 
Herbarium), either as regards thallus or spores. ‘The 
three other forms would probably be referred as “new 
species ”’ to the “lichenous” genus Spilonema, or that re- 
ferred to Sirosiphon pulvinatus, wanting paraphyses, might 
possibly be relegated to Lichenospheria. 
An experimental decision of the “ gonidia-question,” so 
far as it relates to these Scytonematous and Sirosiphonaceous 
forms, is surrounded by nota few practical difficulties. A 
sowing of spores upon the alge (as Reess did with Noséoc) in 
a natural condition could only be carried out by an observer 
residing in or close to the subalpine situation where these 
plants flourish, as they could not be * cultivated” elsewhere. 
In order to obtain the spores he would further have, very 
probably, a troublesome preliminary search, and, on the 
other hand, there would hardly be a certainty of the plants 
selected for inoculation being themselves previously destitute 
’ Itzigsohn, in ‘ Hedwigia,’ 1857, p. 128. 
