388 
It is evidently a right conception, in view of the foregoing statement, 
to regard Puccinia graminis (a better name is Dicwoma poculiforme) as 
a representative of the highest development of rusts. But to regard it as 
typical of all rusts, or even of all rusts having «cia, is clearly asking too 
much of an illustration, and likely to involve grave misconceptions of 
structure and relative values. If the most essential features of the rusts 
were to be illustrated by the smallest permissible number of examples of 
common and well known species, I should select Polythelis Thalictri (Puc- 
cinia Thalictri) for the forms without zecia, Kuehneola albida (often called 
Chrysomyxra albida) for the forms with wcia and isomorphic repeating 
spores, and Dicwoma poculiforme (Puccinia graminis) for the highly de- 
veloped forms with secia and heteromorphi¢ repeating spores. 
A wrong conception, which is doing much harm to the taxonomic study 
of the rusts, is the view that seciospores and urediniospores are of the 
nature of conidia, that is, asexual spores, Comparable to the conidia so 
abundantly produced by mapry ascomycetous fungi. Cytological studies 
show, however, that in the rusts the only truly asexual spores, other than 
the basidiospores, are the pycniospores, and to these only can the term 
conidia be applied with approximate accuracy. The sexual process begins 
by the fusion of uninucleated lyphal cells, which immediately, or almost 
immediately, develop some kind of binucleated spore-structure. If only 
one kind of binucleated spore is produced by the species, it is properly 
called a teliospore. Such a teliospore has two nuclei in each cell, derived 
by a short succession of divisions from the two nuclei of the fusing cells. 
These two spore nuclei fuse into one nucleus prior to germination of the 
teliospore, thus completing the sexual process. If more than one kind of 
binucleated spore is produced, the initial kind may be called an zeciospore, 
whatever the morphological structure in which it is formed. It has 
arisen as the consequence of sexual cell fusion, just as in the preceding 
case, and has the physiological character of greatly stimulated growth 
associated with sexuality. This initial seciospere gives rise to a binucle- 
ated mycelium, which in turn generally produces binucleated repeating 
spores of the same or of a different form, and so on, until finally a telio- 
spore is produced in which nuclear fusion takes place, as in the first 
instance mentioned. The sexual process in this class of rusts extends 
from the cell fusion at the base of the «cia through all the succession of 
hyphal cells and repeating spores to the fusion of nuclei in the mature 
teliospore. 
