. Studies in heredity as illustrated by the trichomes of species and hybrids of Juglans, Oenothera, Papaver, and Solanum. Heredity; Trichomes. 52 HEREDITY AS ILLUSTRATED BY TRICHOMES. MEASUREMENTS ON THE TRICHOMES. The measurements which were made on the multicellular trichomes of the pure lines and first g-eneratlon oijuglans hybrids indicate, as above shown, considerable variation in size, but comparative study showed also that the causal relations attending- the variations migfht be traced, or at least surmised. Thus the variations were seen to be associated with the agre of leaf or with th
. Studies in heredity as illustrated by the trichomes of species and hybrids of Juglans, Oenothera, Papaver, and Solanum. Heredity; Trichomes. 52 HEREDITY AS ILLUSTRATED BY TRICHOMES. MEASUREMENTS ON THE TRICHOMES. The measurements which were made on the multicellular trichomes of the pure lines and first g-eneratlon oijuglans hybrids indicate, as above shown, considerable variation in size, but comparative study showed also that the causal relations attending- the variations migfht be traced, or at least surmised. Thus the variations were seen to be associated with the agre of leaf or with the position occupied by the trichomes on the leaf. These conditions were shown to hold gfood for all the plants brought under observation. It followed, therefore, when these facts were taken into account, that comparison between closely related forms was possible. As the studies reported on up to page 42 were made in two successive seasons, 1906 and 1907, there remained the possibility that variations in- duced by seasonal differences might in some degree alter the measurements as given in the earlier studies by modi- fying the development of the hybrids whose ancestors va- ried in climatic experience as well as in blood. There also remained an instance of the behavior of trichomes in re- version to the pure lines to be observed, since no hybrid examined during the earlier course of this study exhibited this phenomenon. The meas- urements to be given presently, therefore, are calculated especially to show two things, namely, (l) whether the trichomes exhibit seasonal variation in size, and (2) whether ancestral characteristics relating to size of trichomes reappear in the second hybrid generation. JUGLANS CALIFORNICA X JUGLANS NIGRA, SECOND GENERATION. Of the several forms of multicellular trichomes, measurements were made on the disk-shaped and on short secreting types only, and of these the latter offered most favorable material and was mostly used. The following measurements,
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