ii] ASCOMYCETES 51 



the cells communicating by means of large pits, and one{Ascobolits furfura- 

 ceus) or more ( Ascophanus carneus, Lachnea cretea, Rhizina undulatd) of them 

 give rise to ascogenous hyphae. This is the characteristic archicarp of the 

 Ascobolaceae and is found also in Lachnea cretea and in Rhizina undulata 

 as well as in Collema piilposiau and some other lichens. Unfortunately the 

 details of normal fertilization are not yet available in these forms so that it 

 cannot be said definitely whether the oogonial region is in Lilt i- or unicellular 

 at the fertilization stage. In many cases fertilization is known to be "reduced" 

 and in the majority an antheridium has not been recorded. In Ascobolus 

 carbonarius, a small, spcrmatium-like, attached cell (the male conidium of 

 Dodge) has been observed in association with the tip of the trichogyne; 

 somewhat similar attached cells have been seen in Collema pulposum\ in 

 other lichens typical, detached spermatia have been described. Here the 

 type of maximum septation is reached and shows a septate trichogyne, an 

 oogonial region sooner or later septate, and a spermatium-like antheridium. 



The second or spherical type may be derived very readily from the first; 

 the genera Ascodesntis and Pyronema are alike in the development of their 

 sexual organs and the structure of their sheath; the significant difference 

 between them lies in the spherical shape of the oogonium in Pyronema 

 which may well be responsible for the absence of septation. The third or 

 scolecitic type could also be derived through an increase of septation and 

 reduction in the size of the antheridium from Ascodesmis; the coloured spores 

 and reticulate epispore characteristic of that genus and of many Ascobolaceae 

 may be, as Massee suggests, a further indication of relationship. 



The sexual apparatus of the Pyrenomycetes culminates in a septate 

 trichogyne, septate oogonial region and detached antheridium (spermatium) 

 so closely comparable with those of the discomycetous type of maximum 

 septation as to suggest some cross relationship between the groups. The 

 very distinct type of ascocarp, however, in Gnomonia, Polystigma and other 

 Pyrenomycetes on the one hand, and in the Ascobolaceae and their allies 

 on the other appears at present to negative this possibility and to indicate 

 rather a case of parallel development. 



In the Laboulbeniales the trichogyne is septate, and the oogonium is 

 unicellular and undergoes septation after the fertilization stage, but, of the 

 row produced, only one cell gives rise to asci. The fertilizing agent may be 

 a walled spermatium budded off externally, or it may be a non-motile mass 

 of protoplasm ejected from an attached organ. 



The detailed development of the lower Pyrenomycetes has as yet been 

 even less studied than that of the higher forms, and all that can be said is 

 that apparently the antheridium is of a simple attached type and that the 

 archicarp is somewhat elongated, often coiled and sooner or later septate. The 

 larger gametangia among these forms would well repay detailed investigation. 



4—2 



