818 



MICROSCOPICAL SOCIETY. 



March I7ih, 1847.— J. S. Bowerbank, Esq., F.R.S., President, in 

 the chair. 



A paper by Mr. Dean, "On the Growth of Fungus in the Stomata 

 of Cactus niger," was read. The author commenced by stating the 

 difficulty which existed in ascertaining whether the stomata of plants 

 were pores, either actually opening to the outward air, or covered 

 with a delicate membrane, or organs possessing no opening at all. 

 He then stated that a circumstance he had observed in a plant of 

 Cactus niger, which was growing in a Ward's case, and which died 

 in the course of the winter, might probably throw some light on the 

 subject. Upon examining this plant, a portion of the surface near 

 the top was found to be covered with small black patches, which, on 

 applying the microscope, presented the appearance of being fonned 

 of tufts of pear-shaped granules attached end to end. Upon more 

 minute investigation it was found that these tufts had their attach- 

 ment in the stomata, and from them proceeded a net-work of fila- 

 ments, spreading in every direction into the body of the plant, and 

 breaking up its whole structure. These filaments vary in size from 

 the T ^^oo to the igooo th of an inch. When they pass through the 

 stomata their character alters, as they then bear fruit, either single 

 on short peduncles, or attached end to end, frequently to the number 

 of six or eight. Another plant (a Stapelia) growing in the same case 

 had a few weeks before been almost suddenly destroyed by an 

 unknown cause, which appeared to proceed from the roots upwards, 

 but which at the time Mr. Dean did not investigate, although he has 

 no doubt that it was the presence of a similar parasite, as he feels 

 convinced that the sporules of the fungus enter by the roots, and gra- 

 dually but rapidly extend themselves upwards, and when the plant is 

 totally destroyed then they protrude themselves through the stomata, 

 as offering less resistance to their progress than any other part of the 

 tough epidermis, and thus proving, in his opinion, that the stomata, 

 if not open, are at most covered with a membrane much thinner than 

 any other portion of the surface, and thus readily allowing these mi- 

 nute fungi to find their way from the interior to the exterior. 



Another paper by the same gentleman was also read, " On the 

 Source whence the Siliceous Cases of Infusorial Animalcules in 

 Ichaboe Guano are derived." After premising that aquatic birds, in 

 addition to fish, feed largely on marine plants, he proceeded to state 

 that on a plant of this kind from Japan, used exclusively in China as 



