^86 Proceedings of the Royal Irish Academy. 



'closely tufted habit of most of these forms contribute to rendering the 

 little dark lateral tubercles usually formed by the apothecia somewhat 

 Teadily overlooked, whilst they might in some forms be even passed 

 over under a low power (the only useful way of searching) as merely 

 Tiidimentary " branches." 



It is matter of regret to me now that I did not at the time bring 

 forward some notes upon these forms before the preparations I had 

 made had become spoiled ; and it is also a matter of still greater regret 

 that I did not secure some di-awings more in detail than the rough 

 sketches I am able to oifer. But as even a chalk drawing on a black 

 board is better than none, so the accompanying figures (PL 6) may serve 

 a temporary^ purpose until better are forthcoming from some source, 

 whilst the figures of the spores themselves may be accepted as accurate. 



I at once assumed from our knowledge of Ephehe pulescens, coupled 

 with the additional fact of having found apothecia in Scytonema, Sirosi- 

 phon, Stigojiema (^mamillosum), that these genera and probably the 

 whole of the Scytonemacece and Sirosiphonacea, could be no longer 

 properly accounted algse, but should be relegated with Ephebe to the 

 lichens. 



But another and a different solution is put forward now-a-days by 

 Professors de Bary and Schwendener, and those (Reess, Bornet, Treub, 

 and others) who accept the new doctrine of the nature of lichens. It 

 has, as is well known, been previously long supposed that, assuming 

 the gonidia to be really organs of the lichens, these may here and there 

 (and by no means unfrequently) become detached from the parent plant, 

 and, under conditions unfavourable to their forming a new lichen, 

 carry on an independent (probably abnormal) alga-like existence ; and 

 hence that many of the so-called unicellular and some of the filamen- 

 tous algal growths, which may have been regarded as specifically dis- 

 tinct organisms, should really be expunged the list of independent 

 plants. On the other hand, Schwendener and the new school hold that 

 the " lichen-gonidia " are veritable unicellular, or, as the case may be, 

 according to the type of lichen, filamentous algae which vegetate within 

 the lichen-thallus as the serviceable (assimilating) host plants of a 

 parasitic ascomycetous fungus, the " lichen-hypha." A resume of 

 the whole question, of the views put forward and the arguments 

 adduced, so far as the discussion has reached, both for and against, 

 I have recently endeavoured to biing together,* and it is hence super- 

 fluous to attempt here to recapitulate the particulars and points of his 

 hypothesis, except as they bear upon the group immediately in question. 



In his able and interesting work on the ' ' Gonidia-f onning Algal- 

 types,"! ^'^^ beginning with the " Phycochromaceous " series [Nosto- 

 cliince, Nag.), Schwendener places the Sirosiphonacece rn. the front rank. 



* "Quart. Journal Mic. Science," vol. xiii., N. S., p. 217; also vol. xiv., p. 115, 

 in which places the references to the various authors are given. 



t Schwendener: " Die Algentypen der Flechtengonidien," Basel, 1869. 



