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Summary. Nicotiana glutinlosa aiid pinto lbean seedlinlgs (Pliaseoluis v/lgaris) were exposed for short periods (3 days or less) to high concenitratioins of NO, mllg/nii3 to compare the resultinig leaf lesions with ozone damiiage prodtuced at conicentratiolns of 0.43 to 0.86 ng/iM3. Althoutgh the saimie physiological age leaf tissue was daniiaged by both toxicanits, damage cauise( Ny . was unlike that caused by Ozone. P)into bean (P/iascoli/s zvul/gris) aind Pearsoni improved tomato (L!vcopersiwoii esclIlentuhm) seedlinigs \sere conitinuotusly exposed for 10 to 22 days, to low concentrations of NO2 (less thanl 1.03 mg/rn3). rhese eXpOsures Cauised signlificant gro\wth suppression. increase in green color (total chlorophyll coltentit), anld distortioii of leaves.\itrooen oxi(les are emiiitted to the atmlosphere in large quantity froml the many combustion sources in our nmechatnized societv. The estimated daily emis-.Sion for Los A.ngeles in 1963 was 660 toIns of which ap)l)roximately 60 % was fronm vehicular sources (1).Maximlumii meastured concenitrations exceeded 3.0 ppm (6.16 mg/nm3) at times and reached a peak of 3.93 ppm (8.0/7 mg/ni3) NO,, but generally conicenitrations were well below 0.5 ppmi (1.027 mIg/ni3) with the highlest levels occurring (luring the night (2). The involvemiienit of NO., in )hotochemical reactioins in the atino.phere was responsible for reductioll in conlcentration dluriing daylight hours. Because of this reaction Thomas (9) stated that it was unlikelv that atmosph)lleric concentrations of nitrogen )xi(les will ever accumu11l]ate to a le\-el that w,Till cau.se significant plaint damage. Benedict and( BIreen (4)

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The growth and development of the cotton plant is sharply curtailed during periods of limited water supply. During such periods the plant wilts severely but it loses few leaves and again resumes growth when water is available. As originally undertaken the investigation reported in this paper had as its object the finding of whether cotton belongs among those plants that gain in carbohydrate levels under conditions of drought or among those that lose. Stated otherwise, is photosynthesis greater or less than utilization during periods of limited moisture supply? This general question bears on the mechanism of drought resistance, on possible causes of the reported (18) high boll shedding rates in dry seasons, and, finally, on the relation of carbohydrate supply to the susceptibility of the cotton plant to Phymatotrichum root rot in dry summers (9). Investigations are in progress on relations of carbohydrate levels and drought to the properties of cotton fibers. The initial objective is dealt with in this paper by assembling the chemical data that have accumulated during the course of collateral inquiries.Review of literature No one, at least in recent years, has undertaken a general review of the literature on the influence of drought on the accumulation of carbohydrates in plants. The summary that follows does not include all of the available references nor does it include the many observations on the reactions to wilting in detached leaves. It does, however, serve to illustrate the marked diversity between plants in their carbohydrate responses to drought and, also, the fact that there is a marked diversity in the reaction between tissues within given plants. Several opinions on the relation of carbohydrate accumulation to drought resistance are cited and there are included a few references to the effect of drought on the relative growth of roots and plant