116 JOURNAL OF THE 



appearance in miniature of a heavy field of grain after a driving 

 storm, when the stalks of grain are twirled in all directions and 

 matted in inconceivable ways. 



When very large lateral "clubs" are formed, as on the tap root, 

 the tracheal tissue is turned in an outward direction and curved 

 in various ways. But even then it is confined to more or less 

 recognizable bundles, is rarely sharply curved, and never is 

 wreathed around the plasmodia as around the cyst in the root- 

 gall. 



COMPAllISON OF THE RoOT-GALLS WITH THE "TuBERCLES" 



or" " Wurzelknollchen" of Leguminous Plants. — To 

 remove all possibility of a confusion of the root-^j^alls with the 

 tubercles (or Wurzelknollchen) of the Leguminoaeoe, which has 

 probably sometimes occurred, this comparison is introduced. 



These tubercles, which recent experiments* seem to show play 

 an important role in the acquisition of atmospheric nitrogen by 

 leguminous plants, are irregularly oval enlargements of the 

 roots, from the size of a pin-head to a large pea, or sometimes 

 elongate or clavate and very much branched and convoluted. The 

 root-galls will usually not be mistaken for the tubercles by one 

 familiar with these bodies. The tubercles are forn^ed only on 

 the verv vouno^est roots, so that thev are connected with the root 

 from which the diseased one branch by a very slender attach- 

 ment. Sometimes, however, the attachment is very stout. Usu- 

 ally the surface of the tubercle, though it may be greatly con- 

 voluted or lobulated, is smoother and does not present the scurfy 

 or cracked appearance so common, especially in age, on the surface 

 of the root-galls. The root-galls may occur on proportionately 

 large roots, and in a majority of cases the attack is niade some 

 distance from the end of the root, so that the root continues to 

 grow beyond the gall and several galls may be found on the same 



*Atwater, W. O. Attnospherie Nitrogen as Plant Food, Hulletin No. 5, Storrs' School 

 Agr. Exp. Station Conn., Oct., 1889. 



Bertholet, INI. E.\perience.s Nouvelles sur la fixation de Pazote par certaine.s Terres 

 Vegeiale.s et par certaine.>< plantes. Ann. de chim. et de Phv.s. Cme serie, T. XVI, Avril, 

 1889. 



Hellriegel und Wilfarth, Unter.sehungen uber die Stickstoffnalirung der Gramineen 

 und Leguminosen. Beilagehaft z. d. Zeitsch. d. Ver. f. d. Kubenzucker-Iud d. 1.). R. Ber- 

 lin, 1888. 



Abstract in Bot. Centralblatt, Bd. XXX IX, pp. 138—143, 1889. 



