Some recent work on the cytology of fungus reproduction 
263 
fuse. The teleutospore on germination gives rise to a promycelium which 
bears uninucleate sporidia. The sporidium produces a uninucleate mycelium. 
The process by which the uninucleate mycelium becomes binucleate was 
first described by Blackman (Phragmidium violaceum , 1904). He found 
that in the young aecidium the uninucleate hyphae arranged themselves 
in parallel rows perpendicular to the surface of the leaf. The end cells 
were sterile but the penultimate cells became binucleate by the migration 
of a nucleus from a sub-adjacent cell of a neighbouring hypha. Christ¬ 
man (1905) showed that in P. speciosum the binucleate condition arose 
by the breaking down of the cell wall between two adjacent penultimate 
cells. Further work has shown that the method described by Christman 
is much the more frequent. Olive (1908) tried to harmonise the two 
results but certain investigators hold that where migration takes place, 
as described by Blackman, the phenomenon is purely pathological. 
Maire (1911) in an interesting paper on the biology of the Ure- 
dineae , incidentally mentions that on re-examining his slides of Puccinia 
Bunii he finds that the binucleate condition seems to arise by Christ¬ 
man’s method. The cells are so intricate, however, that it is impossible to 
distinguish details. 
Several species with incomplete life cycles have been studied. One 
of the most interesting cases is that of the genus Endophyllum which 
does not possess teleutospores. Hoffmann (1911) has worked at a species 
of this aberrant genus, E. Semperviri. Maire (1900) had previonsly in¬ 
vestigated this species as well as E. V alerianae-tuberosae , while Sappin- 
Trouffy (1896) had worked at E. Euphorbiae silvaticae. In the first 
and last of these species the process described was identical. Binucleate 
aecidia are formed. These germinate and the nuclei divide to form the 
four nuclei of the promycelial cells. The nuclei pass into the sporidia 
and there divide previous to germination. The account given for E. Vale¬ 
rianae-tuberosae is different. The aecidiospores are at first binucleate 
but one of the nuclei degenerates and disappears. When the aecidiospore 
germinates a very short promycelium is formed. The remaining nucleus 
passes into this and there divides, and a wall is formed between the two 
daughter nuclei. The nucleus of the lower cell either degenerates at 
once, or divides, in which case both daughter nuclei degenerate. The 
nucleus of the remaining cell passes into the single sporidium. 
It was difficult to see how these results could be made to fit in 
with the results obtained in so many other genera. Hoffmann’s account 
however shows that in the case of E. Sempervivi at least, the phenomena 
are not so anomalous as was previously thought. A binucleate basal cell 
arises in the young aecidium by the breaking down of the cell wall between 
two adjacent cells in the manner first described by Christman in Phrag¬ 
midium speciosum. The two nuclei divide in the usual conjugate manner, 
forming a series of alternate binucleate aecidiospores and intercalary cells. 
The two nuclei fuse in the ripe aecidiospore. The fusion nucleus undergoes 
reduction either in the spore or in the promycelium which arises from it. 
The promycelium consists generally of four uninucleate cells, from each of 
which arises a uninucleate sporidium. The sporidium on germination 
gives rise to a uninucleate mycelium which produces spermatia (of which 
the fate is unknown) and the aecidia. There is thus a well marked 
alternation of generations, but the sporophyte is considerably reduced^ 
