282 DU, LAUBEE LTKDSAT 03f ARTHOIS'IA MELASPEHMELLA. 



and classification of fungi liaving a liclienoid, and licliens having 

 a fungoid aspect (but all ofwhicli supposed cliaracteristics ap- 

 pear to me to be utterly fallacious when applied to certain indi- 

 yiduai cases) are mainly the following : 



1. Presence of gonidia in the thallus. But a large group of 

 Lichens is athalline — that, to wit, in which the apothecia (with or 

 without spermogones or pycnides) constitute the plant, and are 

 parasitic on the apothecia or thallus of otjier, generally higher. 

 Lichens. Li such cases there can be no gonidia. It is neces- 

 sary, however, to distinguish the apparent from the real absence 

 of a thallus. Though apparently absent, the thallus of a Lichen 

 may really exist in the form of a few scattered gonidia, to be dis- 

 covered only by careful microscopic examination of the super- 

 ficial fibres of the wood, or particles of the stone, whereon the 

 apothecia occur. This is, perhaps, one of the most rudimentary or 

 simple forms of thallus. It may also, though apparently absent, 

 be hypophloeode, consisting of a few gonidia associated with a 

 meagre mycelioid (medullary) tissue, developed in, or under, the 

 tree-bark on which the apothecia are seated. The thallus is either 

 absent or evanescent, or hypophloeode or rudimentary, [for in- 

 stance] in a large proportion of the species of the genera Verruca- 

 ria, ArtJionia, Opegrapha, Graphis^ and Lecidea. And, on the other 

 hand, Nylander, who of all living lichenologists has the widest 

 acquaintance with the Lichens of every part of the world, points 

 out that certain other Lichens have no gonidia {Odontotrema, 

 'Myriangium^j Lecidea luted) ^ though this is, perhaps, a strong 

 argument for transferring them to the Fungi, in which case their 

 absence would form no exception to the rule ; while some plants, 

 which he considers Fungi, possess gonidia {Stictis pallida), m 

 which case the exception might also be abolished by retaining the 

 plant as a Lichen {Leeidea). Currey, however, remarks [letter 

 Sept, 1865], *' Gonidia are absolutely unTcnotcn in Fungi) so 

 that their existence would fix the true nature of the great mass 

 of the Lichens, unless I am mistaken in my notion of their con- 

 stancy" f. 



* M, 



__ Durim, Mnt. & Berk., Kyi. Synopsis, p. 10. Bnt Mynangium is so 

 exceptional in its whole structure, that, if it does not properly belong to the 

 Alg(Ey it would find an appropriate place in my provisional group of Algo' 



lichenes. 



t [Bodies supposed to l>e of the nature of gonidia have, However, been 

 noticed by Bail (Flora, 1857), Zabel (Melanges biolog. St. Petersbourg, t.iii.), 

 and by Berkelry (Introd. to Crypt. Bot. under Emericella), — Sec. L. S.J 



