33 2 Olive. — Sexual Cell Fusions and Vegetative 
a distinct line of ancestors running far back in the life-history of the 
fungus. 
Sappin-Trouffy (’96) also paid little attention to the origin of the 
binucleated condition, as he regarded the fusion of nuclei in the teleuto- 
spore as the most important stage in the sexual cycle. Poirault and 
Raciborski, as well as Maire, opposed this view, since they did not consider 
the fusion in the teleutospore as a sexual act. 
Richards (’96) concluded that the binucleated cells in the Rusts had 
but little significance, since he thought ‘ that they are found in all of the 
other parts of the aecidia, in the hyphae, the pseudoparenchyma, and the 
peridium 1 (p. 260). Richards further considered the aecidium as more or 
less of a morphological unit, for he found at the base of the cup one, 
or occasionally more, large, sometimes multinucleated, cells which, accord- 
ing to him, give rise by budding to the basal cells at the bottom of each 
chain of spores. He was not able to trace the origin of these multi- 
nucleated cells. 
Maire (’00), to whom we are indebted for first pointing out the 
existence of an alternation of generations in the Rusts, finds that in 
Endophyllum the vegetative hyphae are made up of uninucleated cells, to 
the very base of the aecidium. The basal hyphae, as well as the single 
nucleus in each, enlarge greatly. The binucleated condition is now brought 
about, according to him, by simple division of this one nucleus, unac- 
companied by cell-division. The binucleated series starts, then, with 
sister-nuclei. 
Blackman and Christman, notwithstanding their conflict in certain 
important details, agree in the crucial point, viz. that two uninucleated 
cells contribute to the initiation of the binucleated series. The main con- 
tention involves the character of the fusing cells — Blackman maintaining 
that the fertilization in the Rusts is an oosporic process, Christman, on the 
other hand, holding that it is zygosporic. 
Blackman (’04), working with Phragmidium violaceum, describes the 
binucleated condition as arising from a ‘ vegetative fertilization consisting 
of the migration of a smaller nucleus from an ordinary vegetative cell into 
a special ‘fertile, or female’ cell, containing a somewhat larger nucleus. 
Such a reduced sexual process has come about, according to him, through 
the replacement of the now functionless male cell, or spermatium, by an 
ordinary vegetative cell. A simpler ‘ internal 5 fertilization thus replaces 
the former ‘ external ’ fertilization, in which the spermatium functioned. 
He argues that the spermatia are male cells because of their resemblance 
to the spermatia of lichens, and because of their dense nuclei, and their 
small amount of cytoplasm, thus resembling strikingly male cells. He 
finds it impossible to accept the conidial nature of the spermatia, because 
of the difficulty in imagining a process of degeneration which brings about 
