338 BOTANICAL GAZETTE [NOVEMBER 
the first paper he lists additional pathogens which he believes have a mycoplasm 
stage in their life histories, making a total of fifteen rusts 
for which this seen combination of host and fungous protoplasm is claimed 
as proved or suspec 
Additional aes are yosmetind which lead the author to reaffirm, with some 
modifications, his previously expressed belief in the physiological dimorphism 
of the teleutospores, as evidenced by their mode of germination; one sort, in 
moist air, giving rise to long hyphae terminating in chains of conidia; the other 
kind, under the same conditions, germinating in ordinary teleutospore fashion, 
producing basidiospores. The latter, on penetrating the host tissue, give rise 
at once to an intercellular mycelium from which new sori develop in a few days, 
and are therefore the agencies by means of which the rapid spread from plant 
to plant is effected. On the other hand, the conidia discharge their contents 
into a host cell, with the contents of which they form an intimate intracellular 
protoplasmic union, that is to say, a mycoplasm, which multiplies within the 
host, even entering the embryo, thus forming the hibernating stage of the 
fungus. In spring, with the renewal of growth in a dormant plant or the ger- 
mination of a seed, the fungus element separates out from the mycoplasm, 
organizes an intercellular mycelium, and eventually produces sori. Numerous 
observations are reported tending to show that the rapid spread of the disease 
from plant to plant occurs only late in the year, when basidiospores are being 
produced, the summer (conidial) infections not appearing until the following 
season. series of experiments is reported in which the host plants were 
watered with weak solutions of copper sulphate. This resulted in a perceptible 
diminution in the number of summer pustules which appeared, these being due, 
according to the view outlined, to the conidial infections of the previous year, 
the fungus wintering over within the host. The copper solution was of no 
avail against the late summer basidiospore infection. Endeavors to inject 
the copper solution into the leaves and stems were unsuccessful. Without 
attempting to summarize the voluminous data, it may be admitted that the 
evidence seems to favor the view that the fungus may winter over within the 
host tissues. This is by no means a proof, however, that it is in a state of myco- 
plasmic symbiosis with the host. Furthermore, it must be regarded as a serious 
oversight that no notice whatever is taken of the carefully planned experiments 
of BaiLEy,® which seem to point very decidedly to conclusions quite oppos 
to those of Er1ksson. Certainly the facts in the case must be explained, and 
the mycoplasm theory admittedly offers a theoretical explanation. The wide- 
spread opposition to it is based on the feeling that the facts may ultimately be 
accounted for satisfactorily without the theory. If this shall prove to be 
impossible, the mycoplasm “gtr — erect as a oe hypothesis, which, 
however, must be confirmed by f. y ] evidence than has 
et been presented before it can b ded tablished fact.—G. W. Martin. 
6 Ann. Botany 34:173-200. 1920. 
