OLPIDIUM. 



107 



Olpidium brassicae, (Wor.)i { = C/ujtridiiun brassicac, Wor.) 

 Cabbage-seedlings die if tbis fungus finds its way into tbe tissue 

 at the neck of the root. The spherical sporangia are formed at 

 this place, and tlieir long necks project out of the cells enabling 

 the uniciliate swarm-spores to escape. Kesting-spores with a 

 warty thickened membrane occur in the cells of the epidermis. 



Fici. ■Ji. — Chiitridiutn brassicae, Wor. Cell containing three sporangia, two of 

 which are discharging zoospores ; one sporangium is already cniptj-. Resting- 

 spores inside the cells of a cabbage-plant. (Aftei' Woronin.) 



The disease is favoured by moisture, and restricted by dry 

 surroundings. Ground subject to attack should be planted 

 with crops other than cabbage. 



Olpidium trifolii, Schroet. { = Sjfnchijtriiim trifolii, Pass.) 

 Produces deformation of the leaves and petioles of Trifoliniii 

 ■/•('pens. The fungus lives in the epidermal cells. 



Olpidium lemnae, Fisch., in epidermal cells of Lemna. 



Olpidium simulans, De Bary and Wor., in Taraxacum 

 officiiKth'. 



A number of other species inhabit algae, spores, fungus- 

 mycelium, pollen -grains, and eggs of Rotatoria. 



The genera Rcessia, Fseudoljndmm, Olpidiopsis, Flcotrachdm, 

 Ectrogclla, Pleolpidium are parasitic only on lower plants, especially 

 on algae. 



SYNCHYTRIACEAE. 



The whole mycelium divides up into a number of sporangia, 

 which remain together as a sorus. The winter resting-spores 



' Woronin, Prmgsheim's Jahrbuchf. iciss. Botanik, 1878 (Fig. 31). 



