Scientific Intelligence — Botany, 203 



me to think that the dissemination of this minute plant took place 

 by the medium of the atmosphere, which was full oi' its spores. Some 

 experiments with air tight, and partially covered vessels of liquid, 

 placed near the original source, shewed this to be true ; and even 

 now, several weeks after its occurrence, the atmosphere of the room 

 seems to have retained many of the spores ; for liquids placed as before 

 soon contain many of the plants. I state this fact because I think an 

 undue share of importance has been attached to the presence of fungi 

 and algae in various localities, and especially as their being the 

 cause of various coincident phenomena ; whereas, viewed in another 

 light, their presence may, in most instances, be considered accidental, 

 in the ordinary acceptation of the word." 



Dr C. T. Jackson alluded to experiments made of passing the air 

 containing these fungi through concentrated sulphuric acid ; no infu- 

 soria were found in vessels to which air could only gain admittance 

 to a vegetable infusion through the medium, while they were abun- 

 dantly found in infusions to which air had free access. These results 

 confirmed Dr B.'s statement. 



25. Vegetable Physiology. — M.M. Cloes and Gratiolet, operated 

 in their experiments upon aquatic plants, as different species of 

 Potamogeton, Naias, Ceratophyllura, Myriophyllum, and Confervas. 

 The following are some of the results, — 



a. Influence of Light. — The disengagement of oxygen from the 

 green parts of the plants is very rapid in full solar light, insensible 

 in diffuse light, and null in darkness, and in the last condition no 

 carbonic acid is disengaged, contrary to an old opinion, but now for 

 some years correctly understood. With glass of different colours, 

 the effect was greatest with colourless glass, and diminished in the 

 order, red, green, blue. 



h. Influence of Temperature. — The descomposition of carbonic 

 acid by aquatic plants exposed to light under temperature of 4- 4° 

 C, does not commence until the temperature is raised to 15° C, 

 and has its maximum at 30° C. ; and if the plants are in a tempera- 

 ture of 30° C, then on its reduction, action continues even to 10" 

 C. This result corresponds with Chevreul's on the circulation and 

 ascension of the sap of plants. 



c. Influence of the Composition of the surrounding Waters. — In 

 river water deprived of air by ebullition, and containing only car- 

 bonic acid in the same proportion as the waters of the Seine, the 

 water being frequently renewed, the decomposition is at first active, 

 but afterwards diminishes and ceases after four or five days ; and by 

 this time the green colour of the plant has become paler. At first 

 the gas produced is mixed with some nitrogen, the quantity of which 

 goes on diminishing, so that when the decomposition ceases, the air dis- 

 engaged is almost wholly pure oxygen. The total volume of the nitro- 

 gen disengaged is much more considerable than the volume of the plant, 

 and on submitting this plant to elementary analysis, it is found that 



