Blhliogrcqihical Notices. 133 



attention of microscopic observers. It would be .interesting to 

 follow the development of snch genera as Drilosiplion and Schizo- 

 thriv, and trace the changes in the mucous envelope from the early 

 to the mature state of the plants. 



The sixth and last family of the Ptiycocliromophiicece is the Siro- 

 siphotiacece. Omitting Stigonema as a genus " incerta? sedis," it 

 consists of but four genera. Of these, Mastigocladus forms a spongy 

 stratum, and Fischera a gelatinous one, in hot baths in Italy. 

 Hcqxdosiplion is the Folypothrix of Kiitzing, from which it has 

 been separated on account of its mode of ramification, which is 

 supposed to point to a higher grade of evolution. The remaining 

 genus is Sirosiphon or (as it ought perhaps to be called) IlassalUa, 

 remarkable for its multiseriato gloeocapsoid cells. Sirosiphon, as 

 well as the genera of the Scytonemacece above alluded to, was for- 

 merly placed with the OscillatoricB ; and Mr. Berkeley, in his ' In- 

 troduction to Cryptogamic Botany,' remarks of it : — 



" It may perhaps be doubted whether any of the species of tSirusiphon, 

 beautiful as they are, are autonomous. At any rate, their mode of 

 gi'owth and ramification are totally different from those of other Oscil- 

 lutorice. It is a single endochrome which bursts through the investing 

 tube and constitutes a branch, a character by which the species are at 

 once known from Scytoncma." 



Dr. De Bary, in the second volume of Hofmeister's ' Handbuch der 

 physiologischen Botanik,' speaks more decidedly. He says (p. 291) 

 that the thin branches of the thaUus of Epliehe pvhescens represent 

 typical forms of the genus Sirosipdion, that true and unquestion- 

 able examples of Sirosiphon occur in the tufts of Ephehe, and that 

 it may often be seen that they spring like branches from the threads 

 of the Ephehe. 



We come now to Dr. Rabenhorst's third class, the ChJorophyl- 

 lacejn. These he divides into four orders, the Coccophycece, Zygophy- 

 cecr, Siphophycece, and Nematophycea'. The Coccophycea; contain 

 the families PahneUacere, Protococcacere, and VoJvocinecB. Many of 

 the genera in the first two families have been subjected to the same 

 objections as have been raised against so many of the genera in the 

 Chroococcacece, viz. that they are not autonomous, but only states of 

 higher Algae, or perhaps of the gonidia of lichens. Nevertheless 

 (with perhaps one or two exceptions) it will probably be thought 

 that Dr. Rabenhorst has done weU in not reducing the number of 

 genera ; for although many may hereafter prove to be not maintain- 

 able, it would as yet be premature to make any considerable reduc- 

 tion. The present status of several of these genera is very appro- 

 priately stated by Mr. Archer, in some remarks which occur in a 

 paper on Palmogloean Alga3, in the fourth volume of the * Proceed- 

 ings of the Natural-History f^ociety of Dublin.' Mr. Archer is 

 combating the views of Dr. Hicks, whom he seems to suspect of 

 wishing to abolish the Pahnellacece in a body. He (Mr. Archer) 

 says : — 



" Many of the Palmellacean genera produce a very definite structure, 



