236 BOTANY: D. KOSTOFF PROC. N. A. S. INDUCED IMMUNITY IN PLANTS By DONTCHO KOSTOrF. BusszY INSTITUTION OF HARVARD UNIVZRSITY Communicated February 15, 1928 A series of experiments on the family Solanaceae has apparently shown that plant tissues can acquire immunity against certain antigenic agents of other species by some type of antibody production. Normal precipitins were found in leaf extracts and stem extracts and these were tested by Uhlenhuth's ring method (1909). A great variability in amount of precipitation was observed when normal plant extracts 'were tested against each other. Powerful precipitation was observed both when the two extracts tested against each other were from plants of the same genus and when plants of different genera were used; but in certain combinations-particularly with different genera- instead of a precipitation ring, a lytic ring (a ring of liquid clearer than the two components) was observed. The precipitation potency of certain species and genera is increased after grafting; moreover, in certain combinations whose extracts show no precipitin reaction before grafting, the capacity to produce precipitins is acquired during the growth of *e graft unions. The highest acquire- ment of precipitins was found between 30 and 45 days after grafting. Acquirement of precipitins after grafting was observed in the following graft unions: Nicotiana Rusbyi grafted on Nicotiana rustica, Solanum tuberosum grafted on Nicotiana rustica, Nicotiana Sandere grafted on Datura ferox, Nicotiana glauca grafted on Capsicum pyramidale, Lycium Barbarum grafted on Solanum Lycopersicum, etc. The precipitins acquired after grafting are usually specific. Thus extract of Nicotiana Rusbyi immunized against Nicotiana rustica by graft- ing always gave the heaviest precipitate when tested against its antigenic extract, namely, the normal extract of Nicotiana rustica. Then followed in order the extracts of Nicotiana paniculata, Nicotiana glauca, F1 (Nicotiana rustica X Nicotiana Tabacum) and Nicotiana Tabacum. It is perhaps important to note in this connection that the three species Nicotiana rustica, Nicotiana paniculata and Nicotiana glauca belong to the subgenus or section Rustica, while the species Nicotiana Rusbyi and Nicotiana Tabacum belong to the section Tabacum (Comes, 1899). Acquired precipitins of Solanum tuberosum against (grafted on) Nico- tiana rustica precipitate the normal extract of Nicotiana rustica, but not the normal extract of Nicotiana Rusbyi. Sometimes, however, the ex- tracts of Nicotiana Rusbyi immunized by grafting against Nicotiana rustica showed increased precipitation potency over the precipitation shown Downloaded by guest on September 26, 2021 VOL. 14, 1928 PHYSIOLOGY: S. HECHT 237 against the normal extract of Nicotiana alata. The latter Nicotiana species belongs to the section Petunioides and the acquired precipitins of Nicotiana Rusbyi cannot be called "specific" but "heterogenetic." In certain graft unions no acquirement of precipitins was found; viz., Nicotiana Tabacum grafted on Nicotiana rustica, Nicotiana rustica grafted on Nicotiana quadrivalvis, Nicotiana Tabacum grafted on Solanum nigrum, Salpiglossis sinuata grafted on Datura fer0x, Solanum Melongena grafted on Solanum nigrum, Nicotiana Tabacum grafted on Solanum Melongena, Nicotiana Tabacum grafted on Solanum tuberosum, Nicotiana glauca grafted on Nicotiana rustica, etc. A decrease of the normal precipitin potency was observed in the following graft unions: Solanum tuberosum grafted on Datura Wrightii, Solanum Lycopersicum grafted on Datura Wrightii, Solanum Melongena grafted on Datura Wrightii, etc. Comes, 0., Monographie du genre Nicotiana, Topographie cooperative, Naples, 1899. Uhlenhuth, P. u. Weidanz, Technik und Methodik des biologischen Eiweissdifferen- zierungsverfahren u.s.w., Gustav Fischer, Jena, 1909.

ON THE BINOCULAR FUSION OF COLORS AND ITS RELATION TO THEORIES OF COLOR VISION By SuLIG HzCHT LABORATORY oF BioPHYsics, COLUMBIA UNIVERSITY Communicated January 24, 1928 1. Thomas Young's original idea for the mechanism of color vision rests on the fact that by mixing three selected monochromatic parts of the spectrum all kiiown color sensations may be reproduced. Young' supposed that there are three kinds of "fibers" in the retina each producing a characteristic sensation, one of red, another of green and a third of blue (violet). Each type of fiber is sensitive practically to the entire visible spectrum, but the first possesses a maximum of sensibility in the red, the second in the green and the third in the blue. The various color sensations then result from the relative strengths with which the three different fibers are stimulated by the objective light. Few people today suppose that Young's idea, as here given in its simple form or as elaborated by Helmholtz,2 Koenig,3 v. Kries4 and others, is adequate as a complete theory for the mechanism of color vision. The question, however, has often been raised as to whether it can serve even as the basis for a theory of color vision. Downloaded by guest on September 26, 2021