906 



malina scopulovum and favinacea and other lichens. Hooker, in his 

 British Flora, says that he has never found Cetraria sepincola but on 

 wood, but these specimens were found on a block of mica-slate. — Id. 

 454. Remarks on Dr. Ayres' opinion of the Vaucheria. Allow me 

 a few words on the Yaucherise. Your correspondent Dr. Ayres (Phy- 

 tol. 743) seems to wish to annihilate the genus, principally, it would 

 appear, because Vaucher refers his Ectosperma (Vaucheria) terrestris 

 to Protonema velutinum [Agdh.), and which latter is now believed to 

 be a rudimentary moss. I am afraid our Algologists will scarcely 

 consent to this summary mode of dealing with the genus Vaucheria, 

 and I think Dr. Ayres can scarcely be acquainted with the V. terres- 

 tris of our botanists, or he would not follow Vaucher in confounding 

 it with Protonema velutinum. That the whole genus Protonema is 

 composed of the commencement of other Cryptogamia, chiefly mosses, 

 is, I think, generally agreed on by botanists ; but that " the Vauche- 

 riae are the rudimentary states of the mosses, and that the ovoid ves- 

 icles are analogous to granules, and reproduce the primordial state of 

 the moss," is surely an untenable position. What a splendid moss 

 must it be, whose byssoid commencement is one or two feet long, and 

 as stout as a Chara ! — yet if Dr. Ayres' views are correct, such is V. 

 dichotoma : and where have the salt-water mosses come from to pro- 

 duce V. marina and V. velutina ? If Vaucheria is denied a place as 

 a separate genus, so I suppose must Bryopsis and Codium, for these 

 genera are very closely allied to Vaucheria, indeed it is very difficult 

 to separate the latter most singular genus from it by a definite cha- 

 racter. As I am on the subject of these Cryptogamia, permit me a 

 word on the plants associated with the supposed genus Protonema in 

 the group Byssoidese of the Confervoideae, — Hooker 8fc. (Chlorosper- 

 mese, Harvey) ; these consist of the genera Byssocladium, Mycinema, 

 Chroolepus, Trentepohlia, Protonema, Hygrocrocis and Leptomitus. 

 The whole genus Mycinema appears evidently to be altogether com- 

 posed of imperfect Fungi, probably Thelephorse, and Dr. Ayres and 

 others refer M. phosphoreum to a not uncommon state of Auricularia 

 (Thelephora) cserulea. If Chroolepus be retained in the Algae, Mo- 

 nilia, Helmisporium and many other genera must be removed thither 

 from the Fungi ; surely however their structure is completely that of 

 the latter tribe, and Arnott, Carmichael, Hooker, and other eminent 

 Cryptogamists, are of this opinion. It seems to me likely that the 

 Lichen heterophyllus of Smith (Eng. Bot. 2246), a plant which has 

 occasioned considerable peiplexity, and which is doubtfully referred 

 in the ' British Flora' to Cornicularia {Ach.), is a species of Chroole- 



