OLPIDIUM. 



107 



Olpidium brassicae, (Wor.)^ ( = Chytridium brassicae, Wor.) 

 Cabbage-seedlings die if this fungus finds its way into the tissue 

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

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

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

 warty thickened membrane occur in the cells of the epidermis. 



Fig. 24. — Chi/ti'idium brassicae, "Wor. Cell contaiuing three sporangia, two of 

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

 spores inside the cells of a cabbage-plant. (After 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. {^Synchytrium trifolii, Pass.) 

 Produces deformation of the leaves and petioles of Trifolium 

 Terpens. The fungus lives in the epidermal cells. 



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



Olpidium simulans, De Bary and Wor., in TaraoMcum 

 officinale. 



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

 mycelium, pollen-grains, and eggs of Rotatoria. 



The genera Beessia, Psei(dolpidium, Olpidiopsis, Plcotrachelus, 

 Ectrogella, 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, Pringsheim's Jahrhuch f. wiss. Botanik, 1878 (Fig. 31). 



