THE LIC HEX LIFE-CYCLE 1-11 



of quite ordinary Tlielephora-type, with no special characters beyond 

 those of generalized massive Basidiomycetes. These grade biologi- 

 cally from such cases as that of the indigenous Polyporus igniarius 

 on trees, green with intrusive Cystococcus in patches 100 /l deep in 

 the surface-layers, to similar cases of Stereum, with emerald-green 

 colouration due to multitudes of Ghlprella imbedded among the pile 

 of surface-hairs, and the interesting Clavaria mucida of Coker \ 

 described as presenting the initial stage of becoming a Basidio- 

 mycete-lichen. There is little suggestion of the transfer of soluble 

 carbohydrate in these last cases; and though the possibility of a 

 haustorial connection is not invalidated, there is so far no experi- 

 mental proof that the state of Cora is any better ; the assumption 

 being accepted as a stage of parallel biology and morphology. The 

 point which such Basidiomycete examples raise, is that in a parallel 

 group of equally massive hyphal heterotrophic Fungus-types, the 

 special adoption of the Lichen-habit of algal intrusion, or pure para- 

 sitic fungus-attachment, should not be far more general than it is. 

 With equal opportunities for intrusion, this can be taken to imply 

 that the typical lichen-habit is not now to be initiated successfully 

 under normal subaerial conditions, and presumably it never was 3 . 

 Ordinary fungus-hyplne at this period do not casually pick up food 

 from adjacent algal units, and the presumption is that they can only 

 do so exceptionally 3 . Hence the special conditions which initiated 

 the lichen-construction must be sought elsewhere. The successful 

 utilization of helot-algae was apparently restricted to one very special 

 class of transmigrant Fungi at some critical stage in their career. 

 Phenomena of casual intrusion, and every grade of parasitic attack on 

 algae of higher order 4 , may be attempted more or less successfully 

 in other phyla, at different times, with suggestive results ; cf. 

 Gntpliis ■', Lauclatea G , JEphebe, Gosnogonium, and the case of Helvetia 

 and Ascopliyllum never found without associated Mycosphcerella^. 

 The continued survival of a vast series of other Ascomycetous 

 Fungi, which must have been equally transmigrant from pre- 

 sumably very similar marine conditions, and yet present no indi- 

 cation whatever of algal intrusion (cf. Xylaria) 8 , should suffice 

 to show that the algal prototypes of the more distinctive Lichen- 



1 Coker (1904), Bot. Gazette, 37, p. 62. 



2 Cf. Bonnier' s observations on Lichen-spores germinating in association with 

 the protonemata of Mosses (Rev. Gen. Bot), 1889, p. 165, t. 8. 



3 Special interest attaches to the case of the secondary fungus-interloper, as 

 when an ordinary Ascomycete is parasitic on an established Lichen, as Hmnu- 

 stegia Lichenum, and H. Piggottii on Parmelia saxatilis. 



1 Cf. Bonnier (1889), loc. cit. 



b De Bary (Eng. Trans. 1887), p. 399. 



6 Moller (1893), Flora, p. 254 ; p. 277 : summarized in Kerner (Eng. Trans. 

 1895), 2, p. 695. 



'7 Cotton (1908), Trans. Brit. Myc. Soc. p. 95; Sutherland (1915). New 

 Phyt. p. 33. I am indebted to Mr. Marshall A. Howe for drawing attention to 

 the case of fungus with sea- weed in Blodgettia confervoides Harv. ( = Cladophora 

 fuligino&a Kiitz.), and also the cases of Siphonocladus rigidus and Petrosiphon 

 adhmrens. 



8 Cf. also the fine algal form of Cordyceps Taylori: Kerner (Eng. Trans, 1895), 

 2, p. 679. 



