Bihliograj^hical Notices. 131 



had been preoccupied in the Fungi, a reason which would not 

 now be considered sufficient, Dr, Rabenhorst's definition tells the 

 true tale of its origin, " Poli/ci/stis thallo gelatiuoso, initio solido, 

 atate provecta clathrato." It is, in fact, nothing more than a Poh/- 

 ci/stis the gelatine of which has become ruptured and perforated as 

 it has advanced in age. Of Mensmoptedia it may be remaked that 

 it is with difficulty, if at all, to be distinguished from Sarcina *; 

 and if Sarcina (as some good authorities consider) is in reality jiot 

 an alga biit a fungus, the validity of the genus may not unreason- 

 ably be questioned. With regard to Oncobyrsa it appears (wo have 

 not the woik to refer to) to have been placed by Meneghini 

 amongst tlie Nosfochi ncce. ; and if this be correct, the genus can 

 h;irdly be supported after the observations of many past years 

 tending to show the connexion between Nostoc and the CoUema- 

 ceous lichens. 



It would be going into too much detail to discuss at any length 

 the other five families of Dr. Kabenhorst's Pliycoclironiop)]iiiceu'. 

 Doubts may be entertained whether many (if any) of the genera 

 of the OsciUariacece are autonomous, but they may reasonably be 

 retained here in the absence of indications of closer affinities else- 

 where. With regard to one of the genera, viz. Lynghya, it has 

 been stated that it does not o«*cillate, at least when in long fila- 

 ments, which raises a doubt whether its proper position (assuming 

 it be a good genus) is with the OsviUariacea'. Dr. Hicks has 

 suggested (Micr. Journ. n, s. vol. i, p. 164) that Lynyhya mnrah's, 

 Schizoyonium, and Prasiola are but different stages of the same 

 organism ; but it is doubtful how far this view can be supported ; 

 for the two latter are chlorophyllaceous Algte, which would seem to 

 render improbable any close connexion between them and Lynyhya, 

 which is phycochromaceous f. 



With regard to the Nostochacece, the discussions which have 

 taken place as to their nature and affinities would fill a volume. 

 It was long since suggested that most if not all of the plants 

 usually placed in this family are only conditions of gelatinous 

 lichens — an opinion which is now gaining ground, notwithstanding 

 Mr. Berkeley's high authority on the other side, who says, in his 

 ' Introduction to Cryptoganiic Botany ' (p. 141), that he cannot sub- 

 scribe to this doctrine. Nylander is of opinion that the Nostoc of 

 modern algologists, in part at least, if not entirely, may be re- 

 garded as the initial or metamorphic states of the CoUemata ; and 

 he even goes further, and considers that he has added to the lichens 

 various Scytonemata and SiroslpJwnes, such as Synalissa picina, 

 fS. melodermia, ifec.J 



Dr. De Bary suggests a singular alternative theory, which is 



* In the ' Botanisclie Zeitung ' for .Tamiary 10, 1868, Ilallier states 

 that Sarcina differs from Meriamopccdia in its mode of diAdsion. 



t See some remarks by Mr. Archer in the Proc. Nat. Hist. Soc. of 

 Dublin, vol. iv. p. 273. 



X See ' Notuhe Lichenologicre,' translated bv Leighton in -Vnn. & Mag. 

 Nat. Hist, for November 1808. 



