432 



Prof. M. Ward. On the 



[Nov. 21, 



intra-cellular filaments, and the minnte "bacteroids" (which I termed 

 " gemmnles ") were described. Again, I called attention to the re- 

 markable coiling and distortion of the root-hairs at the point of origin 

 and entry of the infecting filament. It may be recalled to mind that 

 I wrote of the minnte brilliant dot at this spot " nnless this dot is 

 one of the above-named 'germs' (i.e., a ' bacteroid ' or ' gemmule ') I 

 do not know what it can be " (p. 548). I also distinctly pointed ont 

 that the twisting of the root-hair at the point of infection might be 

 due to the wall of the root-Lair growing elsewhere, but not at that 

 point. As to the "gemmnles" or " bacteroids "* with which the 

 cells of the inner parts of the tubercle are filled, and their relations 

 to the filaments, I expressed myself (somewhat cautiously it is true) 

 to the following effect. From their curious shapes — those of the 

 letters Y, T, and X, and even more branched figures — I suggested 

 that these bodies propagate by budding ; and from their relations to 

 the swollen ends of the intra-cellular branches of the filaments it was 

 not improbable that they are budded off from these, and multiply by 

 further budding in the protoplasm, &c, of the cells. Owing to the 

 extreme minuteness and high refractive index of these bodies, how- 

 ever, I could not definitely decide as to the method of propagation ; 

 although no doubt existed that they are living " germs," on the one 

 hand, and that they originate from the filaments, on the other. 

 I also pointed out that their presence in the protoplasm of the cell 

 stimulates the latter and makes it resemble a plasmodium (p. 547). 

 Other points of importance will be recalled as we proceed. 



I have now to draw attention to some results of my further 

 researches into this confessedly difficult subject. 



After numerous culture experiments and observations made last 

 year (1888), I have decided to abandon the broad-bean as the subject 

 for histological analysis, chiefly because it takes so long to exhaust its 

 stores of reserve materials ; it was better for the cultures to be made 

 with the pea, the cotyledons of which are so much smaller, and the 

 plant of which is more easily managed in every way in water- and 

 pot-cultures. On the other hand, the tubercles and their contents 

 present no essential features of difference, and, indeed, I may say at 

 the outset, that all that has been described with respect to the tuber- 

 cles of the one is essentially true for those of the other. The position 

 on the roots and the sizes and shapes of the tubercles are the same, 

 and they appear under the same conditions. The colour and general 

 structure of their internal tissues are similar, and the bacteroids of 

 the pea are so little different from those of the bean that it is difficult 

 to believe them specifically distinct. 



But I can offer more conclusive evidence than the above for the 



* Tschirch's word " bacteroids" is a very convenient one, as it does not commit 

 us to any statement as to the nature of these bodies. 



