46 JOURNAL OF THE ROYAL HORTICULTURAL SOCtETY. 



the organism to its environment, whatever that may be ; but if it be 

 asked how or ivhy the living protoplasm is capable of so doing, it is 

 utterly beyond the powers of man's investigation to find an answer, and 

 will probably remain an insoluble problem. 



Mycodomatia of the LeguminoscB. — With regard to the well-known 

 " nodules " on the roots of leguminous plants, these have been studied by 

 various botanists. The following brief account is given in Dr. K. Freiherr 

 von Tubeuf's "Diseases of Plants," p. 101 (1897) : "These tubercles are 

 accessory formations of the primary root-rind and are furnished with 

 vascular bundles connected with the root bundles ; they consist of a 

 cortex of normal cells surrounding an inner large-celled parenchyma with 

 turbid cell contents, consisting of numbers of bacteria [Bacterium radicola 

 or Bhizobmm leguminosanim) (1886)." 



Frank describes the formation of these tubercles,* according to his 

 view, as follows : " The short, rod -shaped microbe forces its way into a 

 root hair or epidermal cell, multiplies there, and is conducted to the inner 

 cortical cells by plasma threads continuous through the cell walls. A 

 rapid division of the inner cortical cells is set up, till a tubercle is formed, 

 which may still further increase by continued cell-division from ameristem 

 at its apex. The bacteria multiply simultaneously, and are transferred 

 into the new cells, where a great change comes over most of them. They 

 enlarge and become club-shaped or dichotomously branched bodies or 

 ' bacterioids.' Brunchorst found the contents of these to disappear at the 

 time of the fruit-formation of the host plant. 



" The great importance c f the tubercles of Leguminosae is that the 

 plants bearing them are capable of taking up free nitrogen from the 

 atmosphere and utilising it, while without the tubercles they could not do 

 so. If Leguminosae be grown in soil rich in nitrogenous food substances 

 the tubercles are not so w^ell developed." Hoiv they fix free nitrogen 

 still seems to be a mystery. 



Turning to Prof. Marshall Ward's papert (of earlier date than Frank's 

 "Lehrbuch") one discovers several points in common with those of M. 

 Gallaud. Briefly, according to him, the impregnation is as follow^s : " A 

 hypha takes its origin from a brilliant granule, presumably one of the 

 granules called by observers bacteria or bacterioids. It passes down the 

 cavity of a root hair, traverses the cortex of the root, beginning to branch 

 where it enters the mass of tissue of the young tubercle. ... It is often 

 possible to see the hyphiP running in the substance of the cell-wall (M. 

 Gallaud detected hyphee of Arum maculatum apparently living on the 

 pectic ' middle ' layer. The hyphae send out branches which end 

 blindly in the cavities of the cells. These branches may be simple or 

 they may have several rounded or tufted bodies (apparently agreeing with 

 M. Gallaud's vesicles and arbuscles), looking like haustoria " (the very 

 purpose assigned to them by M. Gallaud). 



" Whence arise the bacterium-like corpuscles ? They seem to be 

 budded off from the projections of the hypha in the cells in large quan- 

 tities. They then multiply further by budding in the cells. This explains 

 their shapes, which are Y and V shaped. 



* Lehrbuch d. Botanik, 1892, p. 271. 



t On the Tubercular Swellings in the Boots of Vici Faba (1887). 



