128 FROMME: SEXUAL FUSIONS IN FLAX RUST 
a rather small pore which later broadens to permit the entire 
contents of the two cells to fuse. 
The fusions of three and four cells, which are occasionally found 
in Melampsora Lini, are perhaps to be compared with cases of di- 
or polyspermy in animals. The first beginnings of triple cell 
fusions are of rather common occurrence in the group of the 
Conjugatae, but the complete fertile product of such a fusion is 
at least a rare occurrence. De Bary figures one case in Zygnema 
pectinatum of a completed conjugation between three cells, but 
the resulting zygospore has not rounded up, as do the zygospores 
formed by the fusion of two cells, and remains partially distributed 
in a horseshoe form between the three fused cells. As I have 
shown, the triple fusions in the flax rust are functional in the 
production of trinucleated aecidiospores. It would be very 
interesting to determine whether these spores in turn produce a 
mycelium with trinucleated cells. Blackman has also observed 
trinucleated ‘“‘basal cells,’’ aecidiospore mother cells, and aecidio- 
spores in Phragmidium violaceum but did not determine the manner 
in which this condition is brought about. He observed that the 
size of these nuclei is usually somewhat less than that of the 
normal paired nuclei, and suggests that one of the nuclei of a 
binucleated cell may have divided while the other remained in 
the resting condition. He also suggests that a migration of two 
nuclei into one cell would bring about a similar result. In the 
short-cycled form Puccinia Malvacearum, abnormal vegetative 
cells and teleutospores containing three nuclei were found by 
Blackman. Triple and even quadruple fusions are certainly to 
be reckoned with as widespread and fairly common phenomena in 
the sexual reproduction of the rusts. They show a certain 
elasticity in the relations of the gametes, which may be further 
evidence that the sexual process, as at present found, is secondary 
and highly modified from the primitive condition in the group. 
SUMMARY 
The spermatia of the flax rust are produced on septate branch- 
ing spermatiophores, which differ in this respect from the un- 
branched non-septate spermatiophores described by Blackman for 
Phragmidium violaceum and Gymnosporangium clavariaeforme. 
