132 Biliographical Notices, 



"worthy of notice here. After discussing the question of relation- 

 ship between the gelatinous lichens and certain Algse, he says : — 



'' With these data it can hardly be doubted that a large proportion of 

 the Nostochacece and Chroococcace<e are closely allied to the gelatinous 

 lichens, such as Ephehe &c. But the question as to the nature of the 

 alliance remains to be investigated. If I might express my indivi- 

 dual opinion, the reasons for which cannot here be given, I should say 

 that two theories suggest themselves. Either the lichens in question 

 are the fully developed fi'uctifying states of plants whose immature 

 forms have hitherto been placed amongst the Algae, or the Nostochace^ 

 and Chroococcacece are typical Algoe and assume the forms of CoUemata, 

 Eijhehe, Sec, from the fact that certain parasitical Ascomycetes penetrate 

 into them, distribute their mycelium into the growing thallus, and often 

 become attached to the phycochromaceous cells of the former. In the 

 latter case, the plants in question would be pseudo-lichens, similar to 

 the Phajuogams deformed by parasitic fungi, as, for instance, Euphorbia 

 deymier &c." 



The family of the Khndariacere is the most interesting of the 

 six into which the class PhycocliromophycecB is divided. Much doubt 

 stUl exists as to the real nature of the plants composing it ; and in 

 a recent well-known work, the ' Traite Geueral de Botanique,' by 

 Le Maout and Decaisne, the family is swept away with a number 

 of others under the title of Alycie sinirke. Those eminent botanists 

 say (/. c. p. 718) : — 



" We combine under the title of doubtful Algfe (Alyce spuria) a certain 

 number of ill-known genera, which are probably only degraded types of 

 the preceding families ; these are the AlgtB out of which have been formed 

 the Rivulariece, the Oscillariece, the Xostochinea;, the Palmellece, and the 

 Volvociiiece." 



Nevertheless several of the Rivulariacece are objects of great 

 beauty, well deserving of careful study. Some of the so-called 

 genera admitted by Dr. Rabenhorst appear rather too closely 

 allied to one another; but perhaps, until more is known of them, it 

 is safer and more useful to keep them distinct. Dr. Rabenhorst 

 divides the family into two subfamilies — the liivularieie, distin- 

 guished by a rounded thallus which is either gelatinous or indurated, 

 and the MostigotrlcJiice, with a thallus indefinitely expanded and 

 often crustaceous. In the present imperfect state of our know- 

 ledge of the reproduction of these plants, it is impossible to specu- 

 late as to how far any of the proposed genera will be permanent *. 



The Scytonemacece form the fifth family of this class. Most of 

 the genera arranged in it have hitherto been classed with the OscU- 

 lariacecB. Some are remarkable for the peculiarity of the mucous 

 sheath in which the filaments are enveloped ; for instance, the 

 interrupted sheath of Driloslphon and the feathered covering of 

 Arihrosiphon (or Petalonema) are objects worthy of the careful 



* With regard to one of the genera, Inomeria, which is described by 

 Dr. Rabenhorst as " admodum dubium," the reader should consult a 

 paper in the Ann. d. Sc. Nat. 5** ser. vol. vi., *' Recherches sur I'organisa- 

 tion du genre Inomeria, Kg.," by M. Ripart. 



