1915] CURRENT LITERATURE 63 
Mycobacterium, except that there is no evidence of the ae of nitrogen. 
Hitherto pure cultures of Ardisia have been unobtaina 
Von FABER'3 very recently has published further, pcre up various 
minor points, and discussing Miene’s work and his criticisms of the work of 
VON FABER. The most noteworthy result recorded in the latest paper is the 
success of the attempt to synthesize pure cultures of Pavetta and Mycobacterium. 
A symbiosis of the usual kind seen in nature resulted from the inoculation of 
the former by the latter. The luxuriant cultures thus arising seem to show 
clearly that von FaBer was working with the proper symbionts.—H. C. 
COWLES 
Stomatal activity.—ILj1n™ has found that when the stomates of Centaurea 
orientalis are open, the guard cells have an osmotic pressure ranging from 85 
to 108 atmospheres. When the stomates are closed, the guard cells have an 
Osmotic pressure of 13-20 atmospheres. The osmotic pressure of the epi- 
dermal and parenchyma cells of the leaves vary little and approximate that of 
the guard cells with the stomates closed. Similar results were obtained for 
Senecio Doria, Iris pumila, Eryngium campestre, Verbascum Lychnitis, Veronica 
incana, and others. The guard cells with high osmotic pressure (stomates 
open) contain no starch, while the guard cells of low osmotic pressure (stomates 
closed) bear an abundance of starch. Conditions that bring about the closure 
of the stomates, darkness or excessive transpiration, will produce the condensa- 
tion of the sugar to starch, accompanied by the great fall in osmotic pressure 
in about two hours. The reverse process of hydrolysis, accompanied by the 
Sreat rise of osmotic pressure and opening of the stomates, is accomplished in 
about the same time under illumination and low evaporation power of the air. 
If these results are correct, we have here a great contribution to the mechanics 
of stomatal regulation. One would like to know the variation in the osmotic 
Pressure of guard cells that show little stomatal regulation, as is true of certain 
Swamp and xerophytic forms. 
Itjin's has also made an extensive study on stomatal regulation of tran- 
spiration. He used cuttings of plants in potometers and calculated the tran- 
Spiration on the basis of the grams loss of water per 1000 cm.? per hour. While 
the potometer measures water absorption rather than loss, he believes that the 
two quantities are essentially equal in his work, since he has always discarded 
experiments in which wilting became noticeable. He ran his experiments 
in the open, either in an exposed place (the steppe) or in a protected region 
“’ Von Faser, F. C., Die Bakteriensymbiose der Rubiaceen (Erwiderung und 
erganzende Mitteilungen), Jahrb. Wiss. Bot. 54:243-264. i oe 4074: 
_ “It, W. S., Die Regulierung der agen re Zusammenhang mit der 
ae des osmotischen Druckes, Beih, Bot. Centralbl. 32: 15-35- 1914. 
Die Probleme des ree Studiums der Pflanzentranspirati 
A Re. C Centralbl. 32:30-65. 1 
