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dermis, so that mildewed straw when drawn through the fingers feels rough. The 
teleutospores measure from 30 to 60 mk. in length, by from 10 to 20 mk. in breadth. 
Germination takes place only after a prolonged rest of some months, and consists 
in the protrusion of a germ-tube (the ‘‘promycelium” of De Bary) through an 
opening in the wall in each division of the teleutospore. These germ-tubes are of 
a definite length, straight below, usually curved towards the extremity, often like 
the hook of a walking-stick. The upper part of the germ-tube gives off three simple 
branches which taper from base to apex, where each bears a single oval or subreni- 
form hyaline spore from 8 to 12 mk. by 5to8 mk. The end of the germ-tube is 
divided into three parts by septa, from each of these divisions a tapering spore- 
bearing branch arises. The spores, although hyaline, are faintly tinged of a pale 
yellowish hue. These spores, when placed in water, after a short time again ger- 
minate by sending out a slender germ-tube. Now it is upon the life-history of 
these spores, or promycelium spores, as they may for distinction’s sake be called, 
that the main question we have under consideration hinges. If they be placed 
upon a barberry leaf, their slender germ-tubes bore right through the epidermis of 
the leaf into its interior, where they produce a mycelium, which, in the course of 
about eight days, manifests its presence by development of the first signs of the 
Aicidium or Cluster-cup. This is no mere figment of imagination, but a physio- 
logical fact that can be proved by any person so disposed, 
EXPERIMENTS WITH PROMYCELIUM SPORES. 
In the spring of this year (1882) Mr. James Bird, of Downham, kindly gave 
me six small barberry bushes ( Berberis vulgaris), about 10 inches high. On April 
14th, April 17th, and May 9th, respectively, I infected one of these with spores 
from the promycelium of Puccinia graminis from wheat and twitch, and kept the 
remaining three barberries as control plants. In due course the Meidium appeared 
upon the infected plants, the control plants remaining free from cidium, and 
they continued so for two months, when they were cut down, the experiment being 
then ended. If the promycelium spores, however, are placed upon the epidermis 
of a living wheat plant, contrary to what one would expect, they do not enter it. 
De Bary says,* ‘‘The sowing of the promycelium spores gave me, as they had 
previously done,+ the unexpected result that the germ-tubes did not penetrate the 
epidermis of the mildew or teleutospore-bearing host-plant. Upon the various 
parts of Triticum repens, ZT’. vulgare, and Avena sativa, they remained as if they 
had been sown upon a glass plate ; the tubes turned irregularly in the most differ- 
ent directions and died off, the infected grass-plant remaining intact.” 
On April 15th and 17th, I placed upon nine wheat seedlings some of the same 
promycelium spores which were used for infecting the Barberries, and upon May 
7th one of the wheat plants had rust or Uredo upon it. As these plants were, 
however, exposed to the air for fourteen days, an element of doubt is admitted, 
although an equal number of check plants grown in the open air, in the same gar- 
den, remained free from rust. That they did not contract the parasite from the 
* De Bary, Joc. cit., pp. 24, 25. + De Bary, Champ. Paras.. p. 86. 
