38 
LOUIS OTTO KUNKEL 
of the first division of a fusion nucleus. In the Hght of Hoffmann's 
work it seems highly probable that nuclear fusions also occur in the 
aecidiospores of E. Euphorbiae silvaticae. Sappin-Trouffy (17) and 
Maire (12) were probably both wrong in supposing that the nuclear 
phenomena connected with the production of promycelia by the 
aecidiospores of Endophyllum are different from those to be observed 
in the case of teleutospores. 
Although the production of promycelia by the aecidiospores of 
£. Euphorbiae silvaticae and E. sempervivi is well established, certain 
observations have been made which have been regarded as indicating 
that these aecidiospores may at times germinate in the ordinary fashion. 
Thus Nypels (15), Maire (12), and Werth (20) claim that occasionally 
they find non-septate germ tubes which are like the germ tubes produced 
by the aecidiospores of other rusts. Werth noted that the aecidio- 
spores of E. sempervivi produce non-septate germ tubes when immersed 
in water during germination, but that if floated on the surface of the 
water, they produce typical prom^^celia. He seems inclined to think 
that chese non-septate germ tubes can infect the host plant. Hoff- 
mann (8), however, has failed to find any evidence that the aecidio- 
spores of E. sempervivi ever produce the ordinary type of germ tubes. 
It is evident that a further cytological study of these aecidiospores 
is needed to settle this important question. If it could be shown that 
nuclear fusions occur in them and that their tubes typically contain 
four nuclei, which are the product of two successive divisions of this 
fusion nucleus, then, even in the absence of septa, the promycelial 
nature of the tubes would be established. If on the other hand it 
could be shown that nuclear fusions do not occur under the conditions 
mentioned, but that the two nuclei pass out into the germ tube and 
there divide conjugately, we should be compelled to admit that the 
type of germinacion is dependent on environmental conditions. In 
the absence of direct cytological evidence, however, we must be very 
slow to accept such claims. 
My observation that the aecidiospores of Caeoma nitens Burrill 
also produce promycelia, indicates that this rust has a life history 
similar to that of the two species of Endophyllum noted above. Caeoma 
nitens is very widely distributed and produces aecidiospores in great 
abundance. It thus furnishes excellent material for the study of the 
questions that have been raised in connection with the genus Endo- 
phyllum. I have described the earlier work on C. nitens in my pre- 
