THE LICHEN LIFE- CYCLE 1G5 



normal mycelium ; to such an extent, in fact, that it has been 

 mistakenly associated with the spermatogamic mechanism of the 

 Florideaj of the sea, though wholly different from the latter in con- 

 struction and cytology, so far as is known, in the relatively few t} r pes 

 for which it has been at all completely described 1 . There can be no 

 doubt that the organization of these carpogonial ramuli, in terms of 

 uninucleate cell-segments of a uniseriate filament with primary pit- 

 connections, actually reproduces the original cell -mechanism of the 

 algal prototype, and is thus entitled to receive much more detailed 

 consideration 2 . To place two such divergent types of reproductive 

 mechanism, one siphonoganiic, the other spermatogamic, as two 

 divergent variants on the original mechanism of zo'idoganiy, in the 

 same family of Ascomycetous Fungi, may be open to objection; bub 

 too little is known of the various types to draw the line sharply 

 (cf. Polystigma, Lachnea, Xylaria). For present purposes the 

 point to indicate is that spermatogamy, however vague for the Asco- 

 mycetes as a whole, is undoubtedly the dominant method for Lichen- 

 fungi s , as it is also a biological process for securing cross-fertiliza- 

 tion, and is undoubtedly of strictly marine origin. Further, although 

 an autogamous and decadent condition of spermatogamy might end in 

 siphonoganiic approximation, there is much less evidence that sper- 

 matogamy could be evolved via siphonogamy. Tothis extent the con- 

 dition of spermatogamy appears to lie behind the whole of the series ; 

 at the present stage it suffices to introduce the fact that it is generally 

 accepted as primitive for Lichen-fungi. A very similar mechanism of 

 fertilization is still operative through the entire series of the Khodo- 

 phycere ; and if the Lichen-gametophyte presents phenomena of 

 spermatogamy, it undoubtedly inherits this mechanism also from 

 marine ancestors. 



On the other hand, the presumably diploid sporophyte follows 

 identically the ascogenous habit. This phase, already predominantly 

 holoparasitic, takes no part in the new association with alga? ; though 

 algal intrusion even among the asci may obtain in some special cases 

 (as a secondary association in connection with dispersal-function 

 rather than of nutrition — JEndocarpon) . Identical phenomena of 

 apothecial hymenial tracts, scattered on the branches of an algal 

 frond-svstem, reduced to few, or to scattered discs on disc-types of 

 soma, or again presenting the case of immerged perithecia, all follow 

 the normal Ascomyoete pi'ogression, with a degree of parallelism 

 which undoubtedly indicates that this stage of the life-cycle was 



1 Baur (1904) Bot. Zeit., Collema p. 23, Anaptychia fig. 10, Cladonia 

 fig. 40. 



Larbisliire (1900) Prings. Jahrb., t. xi. fig. 3, Pliyscia. 

 Nienburg (1908) Flora, Usnea t. 1, fig. 5. 



2 The spiral coiling is clearly the expression of intercalary extension, and the 

 effect of an outthrust to the exterior, as in the case of the kink in the hair- 

 trichogyne of the Floridese. The essential feature of the cell-units is their iso- 

 diametric character ; the primary pit is emphasized, but a similar pit indicating 

 an older soma on the Floridean model, is characteristic of the hypha? of all 

 higher Fungi (Wahrlich, 1892: Meyer, Bot. Zeit., 1902). 



3 Even in cases where no spermatia have been found; cf. Solorina, Peltigeva, 

 Peltidea, NepJiromium. 



