438 



Prof. M. Ward. On the 



[Nov. 21, 



Experiments with peas and kidney beans enabled him to confirm 

 decisively the discovery that plants in sterilised media, watered with 

 boiled water, develop no tubercles on their roots, whereas those in 

 ordinary soil, or in sterilised media to which infective matter from 

 open soil or from tubercles was added, always formed them. In other 

 words, the tubercles arise by infection from without, as I had demon- 

 strated. He then proved that very young tubercles still show the 

 infecting filaments passing down the root-hairs, " gewohnlichen 

 Pilzhyplien nicht undhnliche Fdden, wehhe, Wurzelliaare und Epidermis 

 durchwachsend, in das subepidermale Gewebe der Wurzel eindringen. 

 Diese Fdden hat schon Marshall Ward in den Wurzelhaaren der Bohne 

 (Vicia faba) beoharhtet und auf Grund dieser Beobachtung behauptet, 

 dassdiefragliclien Knollchenorganismen durch Wurzelhaare in die Wurzel 

 eindringen.^ He describes the appearance of the filaments, their 

 bright look, apparent want of membrane at first, granular contents, 

 &c, all in accordance with my statements in 1887. 



The granular contents gave him much concern ; they are seen as 

 minute rodlets under certain reactions. The branching, piercing of 

 cell -walls, &c, are described as by myself. The only difference here is 

 that Prazmowski believes the rodlets to be the same as the bacteroids. 



He completely confirms my observation that the tubercle arises 

 from disturbances produced in the deeper cortical tissues by the 

 infecting filament, and describes the cell-contents, nucleus, &c, so 

 well known. He also points out that in the very young conditions, 

 the bacteroids are simple rodlets, even in cases where they become 

 Y, Y, X, &c, shaped later. 



To sum up, Prazmowski's account of the whole matter confirms 

 that which I gave to the Royal Society in 1887, excepting that he 

 interprets the origin and nature of the bacteroids differently ; he 

 regards them as produced from the contents of the filaments — as 

 germ-like bodies developed in the interior of the filaments, and not 

 budded off from them. This is hypothesis only, however, for the 

 author expressly states (p. 253), " Direct habe ich Hire Theilungen 

 nicht gesehen, obgleich ich mir die Miihe gab, sie in den verschiedensten 

 Ndhrm.edien und unter den verschiedensten dusseren Bedingungen zu 

 zuchtenr He concludes they can only multiply in the still living 

 protoplasm. 



As to the shapes of the bacteroids and tubercles, Prazmowski's 

 statements agree with those of previous observers, and he also 

 remarks the plasmodium-like appearance of the cell protoplasm at 

 certain stages, as noticed by myself. Some observations on a possible 

 spore formation need not be dwelt upon, as he recognised his mistake 

 in a subsequent paper in 1889. 



He leaves the question as to the origin of the bacteroids by budding 

 or otherwise quite undecided, having failed to satisfy himself whether 



