. Carnegie Institution of Washington publication. 58 HEREDITY AS ILLUSTRATED BY TRICHOMES. <A)5. Four types of trichomes were seen in the pure species californica, nigra, and regia, and in the hybrids Juglans californica Juglans nigra and Juglans californica Juglans regia, but in the species nigra and the hybrid into which it enters an additional form of triehome, not observed in the other plants, was also seen. In addition to these, the regular types, there were also abnormal forms of trichomes which were clearly modifications of those more commonly present, and one type which was essentia
. Carnegie Institution of Washington publication. 58 HEREDITY AS ILLUSTRATED BY TRICHOMES. <A)5. Four types of trichomes were seen in the pure species californica, nigra, and regia, and in the hybrids Juglans californica Juglans nigra and Juglans californica Juglans regia, but in the species nigra and the hybrid into which it enters an additional form of triehome, not observed in the other plants, was also seen. In addition to these, the regular types, there were also abnormal forms of trichomes which were clearly modifications of those more commonly present, and one type which was essentially different from those most abundant. With one exception all types of trichomes were multicellular and glandular. In the second generation of the hybrid Juglans californica Juglans nigra, two of the multicellular trichomes, namely, the short and the long secret- ing trichomes, are composed of 6 and 8 cells, respectively. The sequence of cell-divisions up to the formation of 6 cells is identical, hence the larger triehome may be regarded as a further developed short secreting one, or vice versa, the smaller type may be held to represent an arrested stage in the develop- ment of the long secreting triehome (fig. 20). It does not seem probable that both have Fig 20.— Sequence in cell-division descended from a COmmon ancestor (so to in the short and the long secreting trichomes of juglans. The num- speak) which had intermediate characters, ben give the succession of cell- gince ^ simplicitv Qf thc structure Seems will formation in proper sequence. to preclude this. Of the two other types of multicellular trichomes which occur in the hybrid, and which have from 16 to 32 or more cells, the disk-shaped triehome agrees in the sequence of its divisions with the two trichomes mentioned above in the first two divisions only, and the fourth type of multicellular triehome agrees in sequence with the two trichomes mentioned in the first 3 and possibly the first 5 cell-divisions. The sequ
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