120 rOTATO-FUNGUS. 



1 2 3 



Artotrogus hyduosporui, Mont. (?), from fresh specimens. 1 and 2. From the 

 stem of a Potato ; 1875. Magn. 600 diam. 3. Common form, from a diseased 

 tuber of 1874. Magn. 400 diam. 



are sharp protuberances of the colourless, tolerably thin, external 

 membrane. Within this is enclosed a cell, filled Avith closely-packed 

 protoplasm, also of globular form, but with a smooth surface, and 

 having the structure of a Pythium oospore, with thin, almost colour- 

 less epispore. The globular cells are often considerably smaller than 

 the prickly bag which surrounds them, and then they lie loose in it, 

 enclosed in watery liquid. In other specimens this difference of size 

 is so slight that the prickly envelope is all but completely filled up by 

 the smooth cell. The first of these forms in particular greatly re- 

 minds one of the oogonium of some Saprokgniea (of the genera 

 Saprolegnia and Aphanomyces) which have prickly prominences, and 

 contain a smooth globulai' oospore. In most cases I found these bodies 

 complete, mature, and without any distinct indication of their being 

 attached to mycelium. It was certainly remarkable that they were 

 often situated close to the inner surface of the cell-walls in places 

 where externally the mycelium of Phytophthora undoubtedly ran in 

 the intercellular spaces, or even where a short branch of it penetrated 

 the interior of the cell. All these phenomena were reconciled by the 

 conjecture that the prickly bodies might perhaps be the long-sought- 

 for oogouia of Phytoi^htliora. Jiut on the other hand they might be of 

 (juite different origin, and their former bearers or producers might have 

 disappeared. After long searching in vain, I found in a tuber, in 

 which they occurred along with PytJiium rexatts, an opportunity of at 

 least partially observing their development. They grow on the ex- 

 tremities of the branches of a mycelium which is very like that of 

 P. vexans. The extremity swells out into a globular bladder, which 

 lills with protoplasm, is then separated from its support by a septum, 

 and then sends out, on its entire surface, the slender promiuences of the 

 wall. These are at first flat and blunt, and then grow to be sharp 

 ])rickles. The protoplasm fills them up at first, but ultimately collects 

 itself into the smooth globule which is enclosed in a double smooth 

 membrane. When the bodies are ripe, the mycelium cannot be de- 

 tected. Though I searched diligently, I have never been able, even 

 with approximate certainty, to discover antheridia. I have made 

 many attempts, but in vain, to cause the prickly bodies to germinate, 

 except in one instance, when I saw a specimen which had apparently 

 sent out a luxuriant, repeatedly dichotomous tube. I was unable to 

 observe its further development. 



From all these observations I can determine nothing more than 

 that the star-shaped bodies are the reproductive organs or spores of a 

 Fungus. Their morphological value is uncertain. There is not 



