Sexuality of the Uredineae. 
43 
PUCCINIA ADOXAE, DC. AND UROMYCES SCILLARUM, Wint. 
In these two micro-forms, in which the life-history is similarly 
reduced to its simplest state, young teleutospore sori were examined in 
early spring. In both these cases it was found that the general vegetative 
mycelium showed conjugate nuclei (Figs. 24 and 25). 
In these cases, then, the change to the conjugate condition (i. e. 
the process of reduced fertilization) must take place very early, and the 
point at which it occurs can only be discovered by the careful investigation 
of material from the stage of infection by the sporidium. 
The commonness of the binucleate condition of the sporidium at 
the time of infection might suggest that, in the two cases in question, 
the conjugate condition starts in the sporidium itself. This, of course, 
is possible, but it does not seem probable ; for on the one hand there 
is no evidence that sister nuclei ever become conjugate in this simple 
way, and on the other hand, it has been shown in several cases that the 
two nuclei in the sporidium are not conjugate, but are merely the result 
of a precocious nuclear division to be followed later by a cell-division 
which leads to their separation (see discussion in earlier paper, (1) p. 354). 
It is much more probable that the conjugate condition is produced soon 
after infection by nuclear migration, or cell-fusion, between vegetative cells. 
Uromyces Ficariae, L 6 v . 
In this micro-form (which, however, sometimes exhibits a few uredo- 
spores among the teleutospores), Sapin-Troufify describes the hyphae 
generally as being binucleate, so that it would appear to belong to the 
same category as the two forms just described. The form is not a favourable 
one for investigation, but from our observations the general mycelium 
appears to exhibit single nuclei, but the mass of mycelial hyphae round 
about the teleutospore sorus, as well as those directly connected with 
teleutospore formation, appear to have conjugate nuclei (Fig. 2 6). Thus 
the haustorium in a host-cell close to the teleutospore mass shows clearly 
two nuclei (Fig. 27). 
Though it is difficult to make sure on this point, it is probable 
that we have in this form a condition somewhat intermediate between 
that of Puccinia Malv ace arum and P. Adoxae ; for while the conjugate 
nuclei appear to arise only in connexion with the teleutospores, yet 
they arise earlier than in the first-mentioned form, and produce a general 
mycelium of which part is vegetative and part only teleutospore-forming. 
The existence of young teleutospores with three nuclei (Fig. 26), 
in this form, also suggests that the transition to the conjugate nuclear 
condition has only just taken place. Cells with abnormal numbers of 
