262 



FIXATION OF FRFF MTHOCiFN HV HACTKRIA 



in 1825. TUEVIRANUS (I.), in 1853, was the first to regard these nodules as 

 normal growths, and thirteen years later they were studied by WORONIX (I.), who 

 made the (subsequently important) observation, that the formation contains 

 entirely closed cells filled with living bacteria. In the seventies ERIKSSON (I.) 

 and CORXU (I.) recognised these appendages as metamorphosed lateral roots of 

 perfectly unique structure. 



When regarded in section (Fig. 61), a nodule of this kind is seen at the fir>t 

 glance to consist of two different portions a while or colourless external zone 



Fie. 60. Hoot-nodule of Vicia saliva. 



nil/-, main root : mr. lateral root ; the meaning of 

 tin- other letters is ^iven in Fi^s. 61 and 63. 

 Magn. 3. (.///" /;<>/< rind;.) 



Fir.. 59. -Hoot of Vicia Fain. 



With yoiinu' nodules on most of llie lateral routs 

 ami on the t;ip root. Somewhat reduced. 

 ( .(l'l> r Xlrnxlmrtii r.) 



Fie. 61. Cross-section through a nodule of Vicia 

 saliva, cut aloim the line < in Kiu. 60. 



jir. the primary integument with a few epidermal 



bacteria < rh). 



,>/. the vascular bundles, each \\itli a x\ lem fibre. 

 linct. the. strongly (!eveh>i)ed bacteioidal li~-ne. 



.Ma- u. 10. (Afti r /I';/' ri IK /:.} 



aii'l :tn interior layer, pale red in the young nodule, but, alt rrv.anl.s greenish gi 

 the line of demarcation between them being somewhat sharply defined, and the 

 outline indented like that of a blackberry. It is in the cells of this inner layer 

 that the bacteria now under consideration, and more fully described below, are 

 sheltered; and the layer itself is known as the bacteroidal tissue. On account 

 of these enclosures tin; said root-nodules received from A. 15. FKAXK (11 1.) in 

 1879 the name of mycodomatia (i.e. fungus chambers), an expression that has, 

 however, been abandoned. 



193. Formation and Functions of the Nodules. 



The first to take under consideration the physiological importance of thoe 

 nodules was LACHMANN (1.), who in 1858 defined them of albumen. 



