150 nii: BOTANJOAZ MAGAZINE. LVo i. xxi.no. 250. 



independent of osmotic action. An apparent injurious action, 

 likely due to osmosis, takes place with potassium nitrate at 

 1 20-1 15 mol. and with cane sugar at 1/4-1/3.5 mol. It 

 will be seen that the concentrations of acids, mentioned above 

 as injurious to the spores, are far less than isotonic with the 

 given concentration of potassium nitrate and cane sugar. 



When a capillary tube filled with 1/100-1/150 mol hydro- 

 chloric and nitric acids or 1/200-1/300 mol sulphuric acid is 

 brought into action upon the swarm-spores, we observe, with- 

 in 10-20 minutes, a dense entry of them into the tube, effect- 

 ing " column-collections " of 0.3— 0.4mm. in length. At first the 

 column lies near the mouth but after one hour it shifts to a 

 position deep in the tube, during which no spore is found less 

 deep or at the mouth. This phenomenon expresses the gradual 

 transition of the optimal zone inside the tube. That the length 

 of the column is greater than the breadth of the ring points 

 out that the extent of optimal concentration of H-ions is wider 

 in the tube than in the diffusion zone outside the tube with 

 necessary solution of acids. 



With 1/200-1/300 mol hydrochloric and nitric acids or 

 1/100-1/600 mol sulphuric acid no column-collection may be 

 obtained. The spores which enter the tube are less numerous 

 and distributed more diffusely. If a more dilute solution — 

 1/400 mol hydrochloric and nitric acid or 1/700 mol sulphuric 

 acid— be used it is scarcely possible to recognize a definite 

 collection in the tube. In the preceding (p. 149) we have 

 already ascertained that such concentration is supra-optimal to 

 the spores, so that we do not yet find the reason for non- 

 irritability of spores at the given concentration. Such diversity 

 of result- here obtained should be ascribed, so far as I may be 

 allowed the assertion, to a defect in the capillary method. It 

 must be a very striking error, as it misled us to conceive the 

 SUpra-Optimal concentration, above determined, as below the 

 minima] concentration of acids in attracting the spores. It 

 seems to me that in this connection a consideration of the 

 manner of chemotactic reaction should be necessary. 



