236 DIVISION II.—COURSE OF DEVELOPMENT OF FUNGI. 
is one of this kind. On the other hand, forms like Xylaria, which have Woronin’s 
hypha as a transitory formation only, offer transitions connecting them with Polystigma. 
Amongst the former cases which connect with Melanospora are forms in which at one 
end of the series distinct archicarps are present functioning as certainly asexual (par- 
thenogenetic) ascogonia, and along with them distinct elements ofan envelope; towards 
the other end of the series the difference between ascogonium and envelope-formation 
diminishes till it disappears, and it is only in a more advanced stage of development 
ofthe sporocarp that the formation of ascus and of envelope is undertaken by separate 
elements, which up to that time were apparently uniform with the rest (Pleospora, 
Claviceps). Sexuality therefore is not developed, and in the extreme cases there is 
entire disappearance of primordia of the sporocarp which are homologous with sexual 
organs. In the other series of cases Woronin’s hypha in the Xylarieae can be under- 
stood if we compare it with the archicarp of Polystigma or Collema. It occupies the 
same morphological position, but takes no active part, as far as can be seen, in the 
formation of the sporocarp, and then disappears apparently without having had 
any function to perform, while the formation of the asci is undertaken by neighbouring 
hyphae belonging to the envelope. Here then there is an archicarp or ascogonium 
present in form, but it remains functionless in the sense expressed by these names, 
and the formation of asci falls to the lot of other organs not strictly homologous 
with it. 
These facts all lead to the result, that in these extreme cases we are in presence 
of phenomena, which were spoken of above on page 123 as interruption and restoration 
of the homology. Such a conception would perhaps be rash, if we had not before us 
the clear cases above mentioned of the occurrence of this phenomenon in Ferns and 
Angiosperms ; -but, from our acquaintance with it there, we are led naturally to this 
assumption by arguments which have now been stated. The species with an aborted 
Woronin’s hypha and a formation of asci at the same time are parallel to the 
apogamous Ferns with functionless archegonia and to Angiosperms with an aborted 
egg-apparatus replaced by adventitious embryos; the rest approach nearer to simply 
parthenogenetic apogamy, as seen in Chara crinita and the Saprolegnieae, but 
with the peculiarity that the wap6évos itself entirely disappears in the extreme cases. 
In the above discussions the simple forms which have distinct archicarps, such 
as Eremascus, Erysiphe, and Eurotium, have been treated throughout as forming an 
indivisible group of closely related species, and it has been sought to bring the rest 
into connection with them. More is not at present possible. It ought not by any 
means to be affirmed that all these forms which serve as points of departure are 
connected with the same species outside the Ascomycetes, and that subordinate 
parallel or diverging series do not proceed from individual forms among them inside 
the circle of the Ascomycetes. It was shown above that Eremascus comes near 
the Mucorini, and perhaps special groups of other Ascomycetes connect with 
Eremascus. Podosphaera is nearer on one side to the Peronosporeae, on the 
other to the main body of the Pyrenomycetes, and so on. But at present we are 
not in possession of the empirical material necessary for the enquiry into these details, and 
the main results, as here represented, are not decidedly affected by it. The resemblance 
also in the development of the sporocarps which we have been considering to that of 
the Florideae has necessarily always attracted attention, but whether it points to 
an actual closer affinity must for the present remain undecided; other connection 
than that to which attention has been called above cannot in my opinion be established. 
