170 REV. M. J. BERKELEY. 



in a recognisable form as a constituent of common atmo- 

 spheric dust is recollected. Their presence here accords with 

 Cohn's observation on their conveyance by watery vapour, 

 and suggests that their apparent absence in ordinary atmo- 

 spheric air is due, not to their not entering in it in large 

 quantities, but to the fact that unless the amount of watery 

 vapour present is very great they lose their characteristic 

 appearance, by which, in default of movement, they can only 

 be recognised "■ (p. 52). The addition of dry dust to fluids 

 capable of undergoing putrefaction was followed by their 

 copious appearance, and they also were met with in pure 

 rain-water. It might, however, have been expected that 

 they would have appeared at the commencement of the rainy 

 season, which is generally preceded by a peculiar vaporous 

 condition of the air in many parts of India, but whether 

 this is the case at Calcutta there is no means at present of 

 ascertaining. 



It is not necessary to give at length the general conclusions 

 here, and, indeed, most of them have been anticipated above. 

 The main and most important is the following : — " No con- 

 nection can be traced between the numbers of bacteria, 

 spores, &c., present in the air and the occurrence of diar- 

 rhoea, dysentery, cholera, ague, or dengue, nor between the 

 presence or abundance of any special form or forms of cells 

 and the prevalence of any of these diseases." 



In a more strictly botanical point of view the occurrence 

 of such numerous fungus-spores of such various kinds, in a 

 situation where they could scarcely have been suspected to 

 be present, and the fact of so many of them being in a 

 state of germination is most interesting. It is impossible to 

 say from whence the greater part of them were derived, but 

 one understands at once how it is possible that the same 

 fungus may occur in very different latitudes, provided the 

 climatic conditions are sufficiently favorable. 



It is possible that some of the spores may have germinated 

 on the diaphragm during the twenty-four hours in which it 

 was exposed to the air, but, as Dr. Cunningham says, it is 

 impossible to think that this is the case in such prepara- 

 tions as t. xii, fig. 2, and he believes 'that germination may 

 take place while the spores or sporidia are wafted through 

 the air. And this is the more probable, as they would very 

 rarely be taken up in such a condition. If this be true the 

 germs would settle on their proper matrix in a condition 

 most favorable for immediate propagation. 



Some interesting observations were made on the or- 

 ganisms which appeared in rain-water at Calcutta, algae 



