ELISHA MITCHP:LL SCIENTIFIC SOCIETY. 113 



of the Canebrake Station, Uniontown, Ala., and from Prof. T. 

 M. WatHngton, Abbeville, Ala. 



From the last named place the specimens received were very 

 badly infested with the Heterodera radiciGolaj and with a few of 

 the nematodes which cause the disease described by Prof. Scrib- 

 ner.* I did not find the Heterodera present in the potatoes from 

 any of the other localities. When the potatoes remain in the 

 ground for a long time the fissures in the elevations become so 

 deep and in some places the corky growths are so large and 

 prominent as to be easily distinguished from the appearance of 

 ''scab" in any of the potatoes the writer has seen. In Plate I 

 the upper left-hand figure re})resents the very early stages of the 

 disease caused by Heterodera radicicola, while the upper right- 

 hand figure represents one which has long been infected. 



Comparison of Root- galls with ''Club-foot" of Cab- 

 bage. — It will be of great interest to compare the diseased con- 

 dition of the cabbage roots caused by Heterodera radicicola with 

 the disease of the roots vulgarly known as ^' club -foot ^^ of cab- 

 bage, since in many respects the external characters are very 

 similar, while the two diseases are caused by very widely differ- 

 ent organisms. The nne which causes root-gall, Heterodera radi- 

 cicola, is, when compared with organisms of a lower grade, an 

 animal of quite a complex and high organization. The one which 

 causes "club-foot" is one of the slime moulds, a plant of the 

 very lowest organization, called by Woronin,f who first discov- 

 ered it to be the cause, Plasmodiophora Brassicce. This para- 

 site, when in its mature state, consists of numerous very minute 

 rounded bits of protoplasm, each independent and protected by 

 a thin covering or wall. These remain in a resting condition 

 through the winter in the diseased roots or in the soil. In the 

 spring by decay of the roots these spores are freed. Under 

 proper conditions of temperature and moisture they absorb water 

 until the wall cracks and the bit of protoplasm is set free as a 

 swarm cell; that is, a microscopic bit of plastic protoplasm with 



*Bulletin Agr. Exp. Station, Tenn., Vol. II, No. 2, 188G. 



fPringsheim's Jahrbucher fur wissenschaftliche Botanik, Vol. XI, p. 548. 



