1889.] PUBLIC DOCUMENT — No. 33. 135 



cause the disease. He describes in detail the structure of 

 these masses, as he understands them, but has not seen the 

 supposed parasite in its active state. He names the organ- 

 ism Spongospora jSolani, and regards it as closely related to 

 Plasmodiophora Brassicae, discovered by Woronin * in 1877, 

 and now generally regarded as the cause of the so-called 

 "club foot" or "stump root" disease of cabbages and 

 turnips. For a better understanding of Brunchorst's theory, 

 it may be well to give here a very brief account of the " club 

 foot " parasite. 



On emerging from its resting state under the influence of 

 favorable conditions for vegetation, it appears as an almost 

 inconceivably tiny, naked mass of protoplasm, with the 

 power of moving or creeping about in moist soil. Here it 

 may attack a young root of either of several plants of the 

 Mustard family, most commonly of a cabbage or turnip. 

 Penetrating a surface cell, it lives and grows at the expense 

 of the contents of that cell, moving on to another when the 

 first is exhausted. Cells thus attacked increase in size, in 

 consequence of the abnormal stimulus caused by the pres- 

 ence of the parasite, which often also causes a large increase 

 in the number of cells in the affected region. This hyper- 

 trophy produces the characteristic swellings which give the 

 disease its name. As a result of the growth and fusion of 

 the protoplasmic masses of the organism, many of the root- 

 cells become at length filled by them. Each of these masses 

 separates, toward the close of the season, into numerous 

 very small globular ones, and each of the latter secretes a 

 wall or coat about itself. In this condition the organism 

 can survive considerable extremes of cold or dryness, and 

 can await the recurrence of favorable conditions. When the 

 weather again permits, the walls or coats crack open, and 

 the contained bits of protoplasm emerge from their rest, 

 each one taking up its active life, and repeating the cycle 

 just outlined. Brunchorst believes the history of his Spon- 

 gospora to be very similar to the above, differing chiefly in 

 the fact that the numerous masses, into which the parasitic 

 contents of one cell divide, remain angular and closely 

 compacted into a spongy structure, instead of becoming 



* I'ringsheim's Jahrbacher fiir wissenschaftliche Botanik, vol. xi, p. 5l8. 



