24 
V. H. Blackman. 
conidial nature of which was assumed. These workers, however, 
showed that a very peculiar condition was to he observed in many 
stages of the Uredineae, in which the nuclei were always to be found 
closely associated and dividing in pairs (the so-called conjugate 
nuclei) and arranged in binucleate cells. Sapin-Trouffy carried the 
matter further, and stated that the following, very interesting cycle 
of nuclear development, was to be observed in the Uredineae having 
the requisite number of spore forms. The mature teleutospore is 
uninucleate and gives origin to uninucleate sporidia from which a 
mycelium with uninucleate cells arises (i.e. the nuclei are single); 
on this mycelium spermogonia with uninucleate spermatia arise, 
but in the young aecidium the nuclei become paired with the result 
that the aecidiospores contain two nuclei. This paired condition of 
nuclei is then retained throughout the ensuing mycelia and uredo- 
spores up to theteleutospores, which in the young state are binucleate, 
but later become uninucleate by the fusion of the two nuclei. 
This process of fusion Sapin-Trouffy considered to be of the nature 
of a true fertilisation. 
In these important observations, however, very little attention 
was paid to the spermatia or to the exact method of transition from 
the condition of single to that of paired nuclei, a very peculiar 
method of nuclear division was also described and the figures were 
of a somewhat diagrammatic nature. It thus seemed important 
that the life-cycle should be worked out in detail in a few forms, so 
during the last two years investigations have been carried out on 
Pliragmidium violaceutn , Wint. (probably identical with P. Rubi 
Wint.) and on Gymnosporangium clavarineforme , Rees, with results 
which seem to throw very considerable light on the sexuality and 
life-history of the Uredineze. A short account only is published here ; 
the full paper, with figures, will appear later in the Annals of Botany . 
The spermatia were carefully investigated in these two forms 
and they were found to possess very striking characters,—a thin 
cell-wall, no reserve material, a very large nucleus with no nucleolus, 
and cytoplasm greatly reduced in amount. These characters are 
certainly not those of conidia, but on the other hand are very 
clearly those of male cells. When the special cytological features 
of the spermatia are considered in connection with their close 
association with the aecidia, 1 their total lack of infecting power and 
'The appearance at about the same time as the very effective 
aecidiospores of organs so structurally ill-equipped for 
the purpose of infection as are the spermatia is certainly 
a strong argument against the conidial view. 
