364 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



views of Dr. Torrey upon many botanical points of interest. 

 Dr. Gray has also given, in the proceedings of the American 

 Academy, the conclusion of his former communication upon 

 Composite chiefly Californian. It contains revisions of He- 

 mizonia, Heleniicm, Microseris, Malacothrix, and several other 

 genera. In the same proceedings appears a monograph, by 

 Sereno Watson, of the North American Chenopodiacece, an 

 order largely represented in the region west of the Rocky 

 Mountains. In an earlier article Dr. William G. Farlow, of 

 Cambridge, details the circumstances of the growth of a fern 

 directly from the spore, without the ordinary preliminary 

 development of sexual organs and fertilization by spermato- 

 zoids. This is a unique example of what may apparently be 

 considered partheno-genesis in plants, a few only partially 

 proved cases of which have before been noticed in some 

 phaenogamous species. 



PERIODICAL FLOW OF SAP IN TREES. 



Baranetzky, of the observatory at Kief, has investigated 

 the periodicity of the bleeding of certain plants and its cause. 

 Hoflmeister was the first who recognized that this phenome- 

 non was one very widely observed among forest trees, and the 

 daily and annual periods of this flow of sap have been exam- 

 ined into by several persons. Among the newer results ar- 

 rived at by Baranetzky, it may be mentioned that he has been 

 able to show that the daily variations of temperature had 

 but little to do with the flow of sap; the latter being as de- 

 cided in trees protected from temperature variations, by be- 

 ing inclosed in the hot-houses of the botanical gardens, as in 

 the trees of the open air. The variations are perfectly regu- 

 lar, attaining their maxima and minima on the same day and 

 at the same hours, and seem to him to indicate that the influ- 

 ence of temperature on the periodicity of the bleeding is, at 

 least by certain plants, not direct and immediate, but of such 

 a nature that it at first becomes manifest some time after the 

 action of that which causes it. By introducing an artificial 

 temperature variation, this idea was brought to a severe test, 

 and it was shown that the temperature had really but little 

 to do with the flow of sap, although it would be hasty to 

 conclude that it hnd no influence whatever. It is only in the 

 case of great temperature variations (for instance, a change 



