LABOULBENIALES 389 



That the food is not rich may be assumed from the small size of most species, which 

 have comparatively few cells. That they are xerophytic is immediately clear if one 

 considers that many Laboulbeniales live on dry legs and elytra of beetles. Physically, 

 their habitat may be damp, as in species on aquatic and swamp insects. Physiolog- 

 ically, the point of food intake is very dry. 



The Laboulbeniales, as all the other asterinoid groups, must have undergone an 

 exceptionally far-reaching degeneration; in contrast to the simplicity of the thallus, 

 there is an astonishingly high development of sexual organs and fructifications. The 

 critical point lay in the ectoparasitism on insects, whose leveling influences have been 

 felt by other entomogenous Ascomycetes and imperfecti; many of them also show a 

 Laboulbenial habit as a convergence phenomenon (Thaxter, 1914, 1920). The 

 meaning of these observations is controversial. Are the Laboulbeniales reduced 

 Florideae and their spermatia really spermatia or are they reduced Pyrenomycetes 

 and, therefore, their spermatia are really only originally conidia? To answer these 

 questions which are of fundamental meaning for the phylogenetic derivation of Asco- 

 mycetes and fungi in general, and not to anticipate, the discussion of the Laboulbeniales 

 was postponed to the close of the class, although it is completely isolated there. 



Their derivation from the Florideae is suggested by the habitual similarity of the 

 Laboulbeniales to some parasitic red algae, and by the type of fertilization by sperma- 

 tia, which in the endogenous forms are at first surrounded by a very thin membrane. 

 This hypothesis is wrecked in the morphology of the gonotoconts, the asci. It seems 

 improbable that so highly a specialized organ which as regards the free cell formation 

 of its daughter cells, the ascospores, depends upon such definite phylogenetic condi- 

 tions (coenocytic gametangial copulation, privileging of certain sexual nuclei) could 

 suddenly arise in the short distance from the Florideae to the Laboulbeniales. 



If one rejects this possibility and regards the Laboulbeniales as reduced Pyreno- 

 mycetes, one is obliged to seek another explanation for the antheridia. The exogenous 

 spermatia of Zodiomyces vorticellarius (Fig. 247, 7) and Rhynchophoromyces rostratus 

 (Fig. 253, 1) and for the oidia of some species of Ceratomyces might be explained as 

 conidia although their germination is still unknown. Morphologically, they are 

 undoubtedly conidia. In any case it is noteworthy that at least in Zodiomyces vorti- 

 cellarius, and probably in Tettigomyces vulgaris, as in Collema pulposum, they must be 

 sought for by the trichogyne. Thus they must have undergone secondarily a definite 

 sexual differentiation. 



The interpretation of the endogenous spermatia is more difficult. In Stigmatomyces 

 Baeri they are formed long in advance of the formation of ascogonia (Fig. 248, 8) and 

 their production is continued throughout the life of the plant, even to old age, when the 

 perithecia have finished development and are discharging ascospores. If one wished 

 to explain this spermatial formation on the young plants as extreme protandry, the 

 continuation of spore formation past perithecial maturity must be confusing; such 

 behavior is shown only by imperfect forms, not antheridia. 



It is equally confusing that the antheridia may arise from either cell of the germi- 

 nating ascospore, while the ascogonia arise only from the basal cell. It must appear 

 still more unusual that in Coreomyces any cell in any appendage may form spermatia. 

 Such a relationship argues for conidial formation, not for antheridia. 



Similar considerations arise in the dioecious forms, the Dimorphomyceteae of the 

 Peyritschielliaceae and the Amorphomycetae and Herpomyceteae of the Laboulbenia- 

 ceae. It may be granted that a figure such as we have for Amorphomyces Falagriae 

 argues strongly for the conception we reject here: we have male and female plants, 

 the former form spermatia, the latter ascogonia^ which are fertilized by spermatia. 

 The two sexes remain connected in pairs because in the ascus the sexually different 

 ascopores already cling together. Unfortunately, this group has not been studied 

 cytologically. 



