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The effcfl of loiupenitiire on the stoinntjtl nioveim'nls lias been studied by about ten different workers (iiiriu}^ the p;ist 40 years. Some of the.se mveslij,'ations -amon^ them one oC mine iStaUeit H(28) -were made early in tbis period, al a time when it was not known that the movements are sensitive even to small water deficits in the leaves, and to sUj^ht chanj,'es in the (X)j content of the air. (Consequently, the experiments were made under conditions that may bave given rise In a water deficit, and to chanfjes in the C();> iu the object chamber. Tbe openiri}.; movements whose temperature-dependence was studied were, therefore, probahly not of a phot(.)active nature only. This ciin explain the discrepancies between the results reported (for a review of the literature, see Slalfelt ]\)i)Vi. ]). ;(7."t).Actually, a tempenifure effect has been definitely established only in one investii^atiou by I.ntlfield (1921), and in one by Wilson (1948). it is not, bowever. apparent from the experiments wbether Ibis eftect was manifested ill phutoiictive opening alone, fir whether it was localized to opening processes of other kinds as well.Loitfield used wetl watered pot plants of alfalfa as the experimental object. After the plants had been kept in darkness i)vernight. they were exposed to daylight in the open air. and to other climatic laetors operative there. Stomatal opening was followed microseopically (Lloyd's method) during the first hours. I he experiments were repeated on days with different temperature. Despite the variable external conditions, a distinct relation was observed l)etween temperature and stomatal opening. Tbus. at 10°C approximately 4 bours were retpiired to reach maximum opening. "At 20°C slightly less ih:ni 2 hours was required, and at 30^ (^ nearly an hour. The bighest ti-mperattire. 34""C. caused complete opening in less than 50 minutes. At freezing and alxiut 40°C, opening does not occur or is very erratic" (p. 57).The definite results obtained in Loftiield's experiments are presumably Phusiol. Plant.. /.>. ;.W2 Phyxlol. Plant.. 15. IW2 [772J

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