illK JOUHNAL OF BOTANY 



aquatic phase 1 . The apotheciurn with freely exposed hymenium may 

 be so Ear regarded as older than the perithecium, in which protection 

 of the developing asci becomes more important than the actual 

 discharge of the spores in free air. On the other hand, many lichens 

 present the perithecial condition 2 , while the general parallelism of 

 organization between a perithecium and a Ploridean cystocarp in 

 biological features of parental protection, as well as of nutrition and 

 ostiolar mechanism of emission for immotile spores, suggests a similar 

 origin in the sea, and Pyrenomycetous Lichens may be equally based 

 on marine prototypes. 



II. The production of numerous small ascocarps scattered over the 

 general surface, margin, or tips of the soma, is undoubtedly more 

 primitive than the restriction of the soma to one large cup in the 

 manner of Peziza, or the enlarged convoluted hymenium of a Morch- 

 ella ; and the former method of aacus-distribution — as implying an 

 indefinite number of parasitic sporophyte-stages, following indefinite 

 production of oogonial ramuli — is again carried out much in the 

 manner of the distribution of the cystocarps enclosing similar parasitic 

 diploid generations among the Floridese. Thus it is evident that the 

 apothecia are commonly associated with end-ramuli of the branching 

 soma ; and when, in the limit, the entire shoot-system reduces to a 

 single axis (as in monaxial Angiosperms, or the case of the Cyead 

 from branched arboreal types), the Peziza-cuip, as also the Agaric- 

 model, present the highly specialized limiting case of a sequence of 

 morphological reduction. In their retention of a primitive con- 

 struction of small scattered apothecia, abundantly produced over a 

 freely branching soma (Cetraria, Time a), the fruticose Lichen clearly 

 antedates the more typical saprophytic Ascomycete; though a multi- 

 branched massive soma with countless peri thee ia still obtains in 

 Xylaria. 



III. Again, it is among the Lichen -forming Ascomycetes that one 

 finds the most remarkable suggestions of vestigial sexual organs, as 

 oogonial and antheridial ramuli, which with the exception of the 

 Laboulbeniaceie, alone among Ascomycetes (and it may be said among 

 all Eumycetes) present any definite suggestion as to the possibility of 

 cross-fertilization, as opposed to decadent autogamy. Indications 

 of a mechanism of undoubted spermatogamy, much in the manner oi 

 the Floridese — though very distinct in cytological details of the 

 un its — present recognizable examples of parallel progression in these 

 widely divergent phyla ; similarly' expressing by the closeness of such 

 convergence a condition of response to similar conditions of marine 

 environment (as in reef-pools), and undoubtedly at the same algal 

 horizon. 



IV. On the other hand, there is no need to labour the point that, 

 though so curiously parallel, the early Ascomycetes and the Floridese 

 present no direct connection in essential reproductive stages, any more 

 than they do in their cellular somatic organization. The filamentous 

 construction of the Ploridean soma, with its mechanism of primary 

 pit-connections, bears no relation to the mycelium of an Ascomycete. 



1 Church (1919), ThalasM(>2)hyta, Bot. Mem. 3, p. 50. 



2 A. Lorrain Smith (1911). British Lichens, vol. ii, p. 263. Pyrenodei. 



