390 Harper.—Sexual Reproduction in Pyronema 
entiation of the product of the egg has taken place in all 
cases. The carpogonium regularly divides into three cells, 
of which only the central one produces asci; and in some cases 
this central cell cuts off a so-called secondary stalk before 
proceeding to the development of asci. In the red Algae, 
too, the egg regularly produces a certain amount of sterile 
tissue in addition to the carpospores, so that from this stand¬ 
point the problem of the relationships of the various forms 
becomes a very complicated one. 
Further, Eurotium, as described by De Bary, shows a very 
close relationship to Pyronema in the structure of the sexual 
apparatus (12), and also an interesting resemblance to the 
Lichens. Indeed, Eurotium forms a very good intermediate 
type between Pyronema and the Lichens in many respects. In 
it we have a coiled female branch made up of several cells, the 
upper one of which conjugates with an antheridial cell. This 
upper cell of the coil may well correspond in some fashion 
to the conjugating tube or trichogyne of Pyronema . The 
remainder of the coil consisting of several cells serves as the 
origin for the ascogenous hyphae, being in this respect similar 
to the ascogonium of the Lichen type. How the fertilization 
is accomplished in this case, whether there is a migration of 
a nucleus or nuclei through the apical cell to the cells below 
as in Pyronema , or whether the lower cells serve as auxiliary 
cells like those in certain red Algae as described by Oltmanns, 
and as Darbishire thinks is the case in Physcia , must be 
determined by further investigation. 
On the whole it is quite certain that we have as yet no 
final evidence as to the relationships inside the group of the 
Ascomycetes. In spite of the vast amount of work which 
has been done, the number of forms which have been fully 
described in all their stages, even from the standpoint of 
their external morphology, is surprisingly small as compared 
with the number which are yet to be worked out. This is 
due chiefly to the extreme difficulty experienced in finding 
the earliest stages in the development of the fruits, which at 
this time are generally buried in the nutrient substratum, and 
