OLPIDIUM 89 



delicate mycelium, in the cortex of the root, 30-33 /x diam., 

 wall 10-12 fj. thick. 



Protomyces pachydermus (Thum.) forms rather prominent 

 brown warts on leaves and leaf-stalks of carrot and dandelion. 



Resting-spores subglobose, wall pale brown, 14-24 /x 

 diam. 



Protomyces menianthis (De Bary) forms small clusters of 

 warts seated on red, then brown, patches, on leaves of Meni- 

 anthes trifoliata and Comorum palustre. 



Resting-spores subglobose or angular, brown, 20-40 /x 

 diam. 



Protomyces ari (Cooke) forms irregular bleached patches 

 on leaves and leaf-stalks of Arum maculatum ; the warts are 

 not prominent. 



Resting-spores subglobose, brown, 14-20 /x diam. 



Protomyces purpurea- tingens (Mass.) forms elongated or 

 broadly effused patches of a red or purple colour on the 

 cotyledons and young leaves of the sunflower and garden 

 specimens of Smilacina. 



Resting-spores -solitary, rarely two, subglobose, 25-28 /x 

 brown wall, minutely warted. 



Protomyces concomitans (Berk.). This pest was described 

 by Berkeley in Gard. C/iron., 1882, p. 397, as destructive to 

 cultivated orchids, appearing on the leaves under the form 

 of somewhat pale, moist spots. 



Resting-spores globose, pale amber. 



I have no knowledge of this parasite, which so far as I 

 am aware has not been observed since its discovery by 

 Berkeley. 



OLPIDIUM (A. Braun) 



Vegetative condition passive naked protoplasm, the pro- 

 duct of one spore. This enters a cell of the host and 

 becomes surrounded by a wall, the contents of which 

 become resolved into i-ciliate zoospores, which escape 

 through a long beak reaching beyond the host-cell. In 

 other instances the cell becomes thick-walled and forms a 

 resting-spore, which in turn gives origin to zoospores. No 

 sexual reproduction. 



The total absence of mycelium and the presence of a 

 long beak to the cell, through which the zoospores escape, 

 are the chief features of that genus. 



