FROMME: SEXUAL FUSIONS IN FLAX RUST 117 
different forms studied, or Blackman’s ‘‘partial cell fusions”’ 
must be regarded as pathological in nature. Kurssanow has also 
observed undoubted pathological migrations in his material aside 
from the normal conjugations. 
Maire (’11) has reviewed the numerous problems in the study 
of the Uredineae and given a résumé of our present knowledge 
of the cytology of the group. He regards the sexual fusions as well 
established for forms possessing an aecidium. In reexamining 
his preparations of Puccinia Bunii, an opsis form, he has been 
able to find the isogamous fusion of two cells to bring about the 
formation of the primary ‘“‘synkaryocyte” but is not able to see 
the stages clearly. He does not regard the question of the isog- 
amous or heterogamous nature of the fusion as of great impor- 
tance and thinks cases may be found of the union of sister cells 
or €ven confirmation of the method of forming a binucleated cell 
originally described by Sappin-Trouffy and later by Maire, in the 
microform, Puccinia Liliacearum. Maire holds that the present 
sexual fusions have replaced a primitive sexuality analogous to 
that in the red algae, in which the spermatia functioned as male 
cells. The interpretation of the sterile cell as a trichogyne he 
considers as extremely hypothetical. He holds that the Uredineae 
and the Basidiomycetes have a common origin, but the latter 
have perhaps lost all trace of sexuality. He favors the view that 
the primitive rust forms had spermatia and teleutospores only, 
and that the aecidiospores and uredospores have been intercalated 
in the life history to provide for rapid distribution. 
Olive, in a recent paper (11), has also discussed the character of 
the primitive rusts and the origin of heteroecism. He also holds 
to the theory that the more complex types were derived from the 
Simpler lepto- and microforms by a progressive development of 
the sporophyte. ‘This is substantiated by analogy with the higher 
Plants. The primitive forms were probably autoecious. The 
alternation of hosts was made possible by the production of 
aecidiospores which are invigorated by the stimulus derived from 
: gig act and therefore better able to make the transition to 
thet 8 than the uninucleated sporidia. This would mean 
(atti), of hosts of the gametophytic stage of the Tusts 
, of the heteroecious forms, were the hosts of the original 
