30 LINDSAY, ON ABKOTHALLUS. 



genus Abrothallus. My results, though in the main corro- 

 borative of the admirable descriptions of Tulasne, lead me to 

 take a somewhat different view of the numbers and characters 

 of the species; while they enable me to rectify or supply 

 various of his minor errors of commission or omission. For 

 example, Tulasne speaks of the " Spermogonise ignotse ; " 

 and, so far as I am aware, no previous or subsequent 

 author (for, in Korber's ' German Lichenography,' pub- 

 lished during the present year, the spermogones are stated 

 " in der gewohnlichen Form bei Abrothallus zu fehlen 

 scheinen" '^) has observed, or at least described, the sper- 

 mogones of Abrothallus, which I have been fortunate enough 

 to meet with several times. But I have other and perhaps 

 stronger grounds for bringing the anatomy of Abrothallus 

 under the notice of British botanists. It is destitute of a 

 thallus; is parasitic on another lining lichen; and is possessed 

 of the accessory reproductive bodies, stylospores, contained in 

 conceptacles resembling in structure and site the spermo- 

 gones, and termed by Tulasne pycnides. In each of these 

 respects, the genus is peculiar and deser\dng of special study. 

 I believe that a knowledge of the origin, structure, and 

 mode of development of the deformations of the thallus of 

 P. saxatiUs, on which the Abrothalli grow, will assist us in 

 explaining the nature of certain so-called erratic lichens, 

 which have been lately discovered. British botanists have 

 very recently been much puzzled to account for the origin 

 of a curious globular Parmelia, found by Sir W. C. Tre- 

 velyan, bowling freely before the wind along the surface 

 of the soil on the exposed chalk downs of Dorsetshire. A 

 careful examination has led me to the conclusion that this 

 wandering Parmelia is merely a hypertrophied condition of 

 the deformed thalli in question. Until within the last few 

 years, botanists were almost unaware of the existence of 

 lichens parasitic on other species. Even yet our knowledge 

 of parasitic lichens is exceedingly incomplete. The list of 

 British species is very meagre ; iDut the patient labours of 

 such men as Leighton, of Shrewsbury, and Mudd, of Cleve- 

 land, are daily adding thereto. As illustrations of British 

 parasitic species, it will suffice here to notice the occiuTencc 

 of Calicium turbinatum, Lecidea inspersa, and Acolivm stiyo- 

 nellum, on Pertusaria communis : Sciitula Wcdlrothii and 

 Celidium fusco-purpureum on Peltigera canhia : Celidium 



* 'Systcma Lichenum Gcrmanige. Die rieclitcn Deutsclilaiids fiiisbe- 

 sondere Sclilcsicns) mikroskopisoli o-epnift, krilisch p:csiclitct, charakteris- 

 tiscli bescliriebeii unci systernatiscli crpordnot von Dr. G W Koerbcr ' 

 J^reslau, ISrjfi. 



