482 EECORD OF CURRENT RESEARCHES RELATING TO 



1. In a largo number of the plants examined drops exude from the 

 leaves at different spots when water is forced in. 



2. In many plants the result of forcing in water is an injection 

 into the intercellular spaces of the leaves, with or without the 

 exudation of drops. This is indicated by the dark green colour of 

 the under side and the transparency of the entire leaf. 



3. In those plants which disjilay both injection and exudation of 

 drops, it is frequently the case that only the younger leaves exude 

 water, while older leaves of the same plant exhibit injection only or 

 both phenomena conjointly. 



Air as a Germ-carrier.* — After a long and very unfavourable 

 review of the labours of previous aeroscopists, including Pasteur, 

 Lewis, and Douglas Cunningham, Dr. Wernich describes certain ex- 

 periments on the action of air-currents upon germs. His apparatus 

 is essentially a modification of that previously employed by Nageli. 

 Filtered air is drawn through or over the germ-containing material, 

 and thence into a vessel containing pabulum, sterilized by boiling. 



He finds (a) that thoroughly dried compact masses contain- 

 ing germs, e.g. slices of potato bearing crusts of Micrococci, and 

 similar incrustations on glass, wire, &c., yield no germs, even to the 

 strongest air-current ; (li) that coarse and fine dust is easily carried 

 over in the stream of air, and the germs it may contain develop all 

 the more surely if they are accompanied by a small quantity of their 

 former pabulum ; (c) that porous bodies of different kinds saturated 

 with putrefying fluids and then carefully dried, yield germs to the 

 air-stream, but slight moistening of the porous body is sufficient to 

 prevent this ; (rfj that slimy surfaces bearing germs may be slightly 

 dried by the current of air and germs then taken up ; (e) that germs 

 are not taken up from a fluid through which air passes if the forma- 

 tion of spray and foam be guarded against. 



The author then discusses the bearing of these results upon the 

 ventilation of hospitals, and concludes that while it is doubtless im- 

 portant as much as possible to avoid stirring up the dust of sick 

 rooms, and to ventilate them by as regular and gentle a stream of air 

 as jiossible, the importance of the air as a vehicle of infectious germs 

 has been much exaggerated. 



B. CRYPTOGAMIA. 



Cell-nucleus in Thallophytes.f — As a sequel to his discovery of a 

 plurality of nuclei in the cells of the Siphonocladiacese,! Professor 

 Schmitz, of Bonn, has carried on a series of similar investigations 

 with regard to the cell-structure in other Thallophytes, especially 

 those hitherto considered to be destitute of a nucleus,§ including, 

 according to A. Braun, the Chroococcaceae, Oscillarieas, Nostochineaj, 

 Palmellaceas, Cladophoreae, and Siphoneae. The following were the 

 most interesting results attained :— 



In the Siphoneae the species especially examined were Codium 



* 'Arch. path. Anat. u. Pliysiol.' (Virchow), Ixxix. (1880) p. 424. 

 t ' SB. Niederrhein. Ges. Natur- u. Hcilk.,' Bonn, Aug. 4, 1879. 

 X See p. 49.3. j See also ante, p. 111. 



