124 



PHYCOMYCETES. 



is very frequent on wild and cultivated Cruciferae throughout 

 the whole world, and causes deformation of shoot, leaf, and flower. 



Fig. 3i.~Cj/xtopus candidta. B, Conidlophores isolated from the cushion ; the 

 coDidia or sponuigia are united by intermediate cells. C, Sporangia breaking up 

 CO form swarm-spores. I), Swarm-sporcs escaping. E, Swarm-spores in motile 

 condition. F, Swarm-spores come to rest and germinating. G, Two germ-tubes 

 entering a stoma of Lepidium sativum ; the stoma is shown from the inside, so 

 that the spores from which the germ-tubes arise are on the outei" surface and 

 unseen. (After De Bary.) 



Fig. 35.— Flower of Radish (RapJianus sativiui) hypsrtrophied by Cystopus 

 candidvs. The much.enlarged ovary stands out in the centre. The anthers ai-e 

 Itfaf-like ; the petals are much enlarged and hang downwards ; the sepals are 

 somewhat enlarged. (Specimen from Botanical Museum of Erlangen, and 

 photographed by Dr. Bruus.) 



The conidial cushions form thick white stripes with a porcellaneous 

 appearance, by which they are easily distinguished from the 

 cushions of Peronospora parasitica often present on the same plant. 



