150 SYDNEY H. VINES. 



vet^etation of the Alga is under these circumstances more active. 

 M. van Tieghem distinguished two kinds of parasitism among 

 Tungi, (1) necessary and (2) voluntary, examples of which he 

 adduced in illustration. In Lichens it is otherwise, the cohabi- 

 tation of Alga and Fungus is a reciprocal parasitism, the Alga 

 probably supplying the Fungus with carbohydrates and being, in 

 return, preserved from desiccation by the investing hyphae. 



To the number of this Journal for January, 1875, Archer 

 contributed a paper ^'On Apothecia in some Scytonematous and 

 Sirosiphonaceous Algae in Addition to those Previously Known." 

 His researches were suggested by those which led Bornet^ to 

 remove Stigonema atrovirens from the Algse and to place it 

 among the Lichens under the name of Ephebe piibescens ; and 

 their object was to discover, if possible, in allied forms the dis- 

 tinctly lichenous fructification — apothecia and spermogonia — 

 which this species of Stigonema had been found to possess. 

 Archer was successful in discovering apothecia in 8cytonema 

 myochrous, as well as in another unidentified form, in two species 

 of Sirosiphon {alpinus and pulvinatus), and finally in Stigonema 

 mamillosuni. He was, therefore, led to assume that these genera 

 and probably the whole of the Scytonemacese and Sirosiphonaceae 

 could be no longer properly accounted Algae, but should be 

 relegated with Ephebe to the Lichens. Archer was unable to 

 detect any hyphae in the species which he examined, though 

 Schwendener had found them in Ephebe and Bornet in Spilunema 

 jiaradoxum and in Lichenospfueria Lenormandl, nor could he 

 discover any spermogonia. 



The next important publication is that of Arcangeli.i In the 

 general discussion of the question which precedes the account of 

 his own researches, he points out that Schvvendener's theory has 

 in its favour the fact that Fungi are parasitic plants incapable of 

 forming chlorophyll so far as our present knowledge extends. 

 He argues that it is not, however, impossible to imagine the 

 existence of plants which, though of a distinctly fungoid nature, 

 may yet be able to form chlorophyll and to assimilate. Lichens 

 undoubtedly resemble Fungi very closely both in their vegetative 

 structure and in their reproductive organs, why then, he asks, 

 may not Lichens be regarded as plants belonging indeed to the 

 group of Fungi but containing chloroj)hyll ? In the Phanero- 

 gams examples occur of natural families, some members of which 

 do, and some do not, contain chlorophyll. 



He brings forward some observations in support of this view 

 which tend to prove that chlorophyll may occur in cells of Lichens 



' " Recherclies sur ia structure de I'Ephebe Pubescens," ' Aun. Sci. 

 Nat,' ser. iii, t. xviii. 



2 ' Sulla questioue del gonidi, Nuov. Giorn. bot. Ital., 1875. 



