igoS] CURRENT LITERATURE 351 



nations of external modifying stimuli and nutritive conditions, in the widest sense, 

 is exceeded. In each ever-sporting variety there is a critical period at which 

 the "normal" or the "sport" condition is determined. If this period occurs 

 late in the ontogeny, the sport appears as a partial variation, as in the five-leafed 

 clovers; and if it is very early in the ontogeny, the variation appears to be in- 



L 



dividual, as in the case of double stocks. 



A sharp distinction is drawn between these modifications and mutations, and 

 Klebs is criticized for failing to keep them separate. This criticism would api)ly 



equally well to many other writers. 



With ever-sporting varieties, many variegate-leaved varieties have a great 

 but purely superficial resemblance. The author recognizes two types of golden 

 modification, one due to disease, the other hereditary. Pedigree cultures with 

 the latter type present striking results in the case of Antirrhinum tnajus pumilum 

 jol. aureis and Pelargonium zonale. In Antirrhinum the cross between any two 

 variegated specimens gives variegated and green in ratio 2:1, of which the green 

 breed true. The conclusion was reached that variegation is in this case a Mende- 

 lian character, in which the union of two "variegated" gametes does not give 

 rise to a successful zygote. In proof of this view, the cross bet^^-een vanegated 

 and green (DR X R) gave in every case the expected ratio 1:1. Ever)- variegated 

 individual is thus a heterozygote, and the problem of the "fixation" of the varie- 

 gated race is the same as that of the fixation of the blue Andalusian race of fowls. 

 In Pelargonium zonale a somewhat similar situation seems to exist, but here 

 the extracted dominants, instead of being entirely incapable of development, 

 appear as pure-white individuals which perish very early, leaving again the ratio 

 of variegated to green, 2DR:iR. — Geo. H. Shull. 



Injury by smoke.-Continuing the studies embodied in the volume published 

 a few years ago on the injury of vegetation by smoke,'5 which treated chiefly 

 of gases, Haselhoff, with the assistance of several colleagues, has been mAesu- 

 gating the effect of the solid constituents of smoke and other factory emanations, 

 which fall as dust, and may injure plants either directly by contact with heir 

 leaves or indirectly through their roots by way of the soil.- Such mvestigat^ns 

 are particularly important in continental countries, where huge factories are otten 

 closely surrounded by cultivated fields. They are of less value m this counUy^ 

 where the cultivation is less close and a strong tendency exists to ^^^ »™ 

 in industrial centers. Yet at any time such data as are here set lortn m y 



guide 



.position even trom simi 

 ^^^^arv in each case 



; sort 01 lactones, su uiai xx, ^^^ ro/QO ^ ^ 



rhUr'^M <N^C\) sulfids NaSO, and Ca(SOJa;, 

 .position. Chlorids (INai^iJ, sum ^ v ^ ^ ^^^ ^^^^^^ ^^ 



and perhaps also sulfates (NaS04) are particularly injurious. 



^5 See Box. Gazette 38:148. 1904 



Flugstaub 



und Pflanzen. Landw. Versuchs-Stat. 67:157-205. P^^^ ^> ^' ^^^^' 



