72 Occurrence of Bacteria (Bacilli) in Living Plants. 



conditioned health), in the renal secretion quite recently 

 passed — yet, strange to say, although the cells of vallisneria 

 have been examined by me hundreds of times, the presence 

 of these organisms has hitherto escaped observation, or 

 been overlooked. I account for this from this circumstance 

 — that the bacilli are minute ; they occupy, chiefly, external 

 cells ; are intermixed with cell contents ; and, lastly, they 

 gradually gravitate to the lowest portion of the cell in which 

 they are to be found, so that the examination of a leaf 

 which has been lying for some time flat on the table will 

 fail to afford evidence of their presence, as they have sunk 

 behind or below the starch and chlorophyl grains in the 

 cell. 



There is, however, another feature for consideration. The 

 plant on which I have been experimenting — and you have 

 before you specimens of it, and they look healthy — has 

 been under confinement or cultivation for a period of three 

 or four years ; and I have also, in examining specimens of 

 leaves living in an open pond, found no bacilli, and we have 

 therefore to consider the conditions of life to which my 

 specimens of vallisneria have been subjected, i.e., in the 

 summer season to a temperature at times, as I have ascer- 

 tained, of 100 degs. Fahr., and a less depth of water than 

 natural. 



The plant as I have seen it in Sydney possessed leaves 

 five to six feet in length, with more than an inch in 

 breadth, and of such thickness that it was easy to cut slices 

 edgeways off it, each slice having an upper or a lower edge 

 of outside cells on the right and left of the observer, so that 

 the central larger cells can be fully exposed for viewing the 

 cyclosis going on in them, besides which it is easy to split 

 the leaf into two layers for the same purpose. 



The greater size of the cells and the easy mode of 

 manipulation conduce very favourably to the examination 

 of this phenomenon, compared with the cells of the European 

 variety of this plant, as I pointed out in my recent visit to 

 England, when I introduced a few living specimens of our 

 Australian form for the special benefit of my colleagues in 

 microscope research. 



It will be well to pursue the conditions of life which 

 have surrounded my specimens. For instance, the pond 

 plant has a darker area in which it grows ; the light sup- 

 plied to it under natural conditions reaches it mainly from 

 above, whilst lateral supply is materially lessened. Compare, 



