124 Murphy.—The Morphology dnd Cytology of the 
might have arisen first and the antheridium applied itself around it (as 
happens in many Fungi), the inside walls of the hypha or hyphae which 
coiled around the female organ then disappearing. This would give the 
appearance which such an antheridium as we have here presents at maturity. 
If this did not occur there seems but one other alternative, that the antheri¬ 
dium arose first and the oogonial incept pushed its way into it as has been 
suggested. To examine the former theory first: The youngest antheridia 
found (Figs. 2 and 3), in which the oogonial incepts have penetrated only 
about half-way through, present no indication of having wrapped themselves 
round the female organ or of having been derived from hyphae the ends or 
sides of which fused to form a single continuous cavity around another 
hypha. It is true that a young antheridium previous to being pierced by 
an oogonium has never been seen. This may be because the stimulus of 
contact with an oogonial incept is necessary for the formation of the male 
organ. In P. infestans oogonia arise independently of antheridia, for the 
latter are most frequently missing (Pethybridge and Murphy, 30 ), and 
perhaps it is so here too. This was the impression of de Bary and 
Woronin ( 5 , p. 85). Two antheridia have been found which were not 
traversed by any hypha. They were well isolated, evidently in relation to 
no oogonium, but they presented all the appearance of being much older 
than developmental stages. It is possible that the oogonial incepts which 
stimulated their formation failed to develop. If this be true, it is easy to see 
that the finding of an antheridium between the time contact takes place and 
the stage shown in Fig. 2, or a little earlier, would be by no means an easy 
matter. Growth takes place at this stage with great rapidity, as Pethybridge 
( 27 ) has shown. Further, it would be difficult to account for the invagina¬ 
tion of the antheridial wall and the partial encasing of the stalk of the 
female organ with a sheath of antheridial origin except on the hypothesis 
that the oogonial incept does pierce the already formed male organ. In 
fine, no evidence whatever has come to hand that the antheridium arises by 
coiling round the young oogonial incept; and if this be merely negative 
evidence it is at least derived from a very large number of observations. It is 
perhaps not a sound argument in the case of such a P'ungus to say that it 
would be unreasonable for the antheridium to encase the female organ 
at such an early stage as to compel the latter to break through it at the 
top, when it might more easily arrive at the position the antheridium holds 
at maturity by encasing the oogonial stalk a little later. 
There is no evidence, then, that this hypothesis is sound and it does not 
explain the observed facts. The only alternative remaining is that the 
previously existing antheridium is pierced by the developing oogonium. 
There can be no question, however, how the oogonium emerges. It bursts 
through the upper wall of the antheridium and forms an oogonium at its 
summit. It can be seen in the act (Figs. 6, 7, c, and 8). This fact is as 
