132 BiUographical Notices. 



Avorthy of notice here. After discussing the question of relation- 

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



" With tlu'se data it can liardly be doubted that a large proportion of 

 the yostovhacv(e and ChruococaiCLHC are closely allied to the gelatinous 

 lichens, such as Ephcbe kQ. But the question as to the nature of the 

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

 dual opinion, the reasons for which cannot here be gi\ en, I should say 

 that two theories suggest themselves. Either the lichens in question 

 are the fullv developed fructifying states of plants whose immature 

 forms have hitherto ot>en placed amongst the Alg;e, or the Nostochaccoi 

 and Chroococcacia are typical Alg;« and assume the forms of CoUcmata, 

 Ephehe, &c., from the fact that certain parasitical Ascomi/cctes 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 Pha^uogams deformed by parasitic fungi, as, for instance. Euphorbia 

 deyener &c." 



The family of the Rivularlacece is the most interesting of the 

 six into which the class Phycochromophycece is divided. Much doubt 

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

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

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

 of others under the title of AJyce sjiurki;. Those eminent botanists 

 say (/. c. p. 718) : — 



*' We combine under the title of doubtful Alga3 (Alycs spuria) a certain 

 number of ill-known genera, which are probably only degraded tA'pes of 

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

 the Rirulariece, the OsciUuriecc, the Nostochinecc, the Palmellece, and the 

 Volvocitiecp." 



Nevertheless several of the lUvulariacexn arc objects of great 

 beauty, well deserA-ing 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. llabenhorst 

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

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

 and the M((sti(jotrichi<e, Avith 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 Avill be permanent *. 



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

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

 lariacec. Some arc remarkable for the peculiarity of the mucous 

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

 interrupted sheath of Drilosiplion and the feathered covering of 

 Arthrosiphon (or Petalonema) are objects worthy of the careful 



• AVith regard to one of the genera, Inomeria, which is described by 

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

 paper in the Ann. d. Sc. Nat. 0*= 8(5r. vol. vi., " Kecherches sur I'organisa- 

 tion du genre Ino/iicriu, Kg.," by M. Kipart. 



