The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . r follows immediately on the seed-leaves(Fig. 76 B). All such cases can often be observed in J/ 0 Tricotxious Races. the same culture from the seeds of a single is especially the case in Anfirrliiniiin iiiajiis andScropJiularia nodosa, in which species I have often pre-ferred as seed-parents, the tricotyls, whose first whorlswere trimerous. Nevertheless they have not, as a rule,proved the better qualified to continue the character oftlie race. Further instances are afforded by
The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . r follows immediately on the seed-leaves(Fig. 76 B). All such cases can often be observed in J/ 0 Tricotxious Races. the same culture from the seeds of a single is especially the case in Anfirrliiniiin iiiajiis andScropJiularia nodosa, in which species I have often pre-ferred as seed-parents, the tricotyls, whose first whorlswere trimerous. Nevertheless they have not, as a rule,proved the better qualified to continue the character oftlie race. Further instances are afforded by Dipsaciissylvestris, Lychnis fidgcns, Dracoccphaluin nioldavicunu Dianthus harbafus and soon. Tn the spring of 1887 Thad some tricotylous seed-lings of Acer Psetido-Plata-niis: two of them are nowhigh trees, whose trunks beartheir branches in trimerouswhorls. The lateral branches ofternary main stems tend, asa rule, to revert to the de-cussate arrangement. Sub-terranean runners, (for in-stance in Valeriana officina-lis) and the secondary stemswhich are produced at theDianthus barbafits), afford,. Fig- 75- FciStts syhatica. Tri-cotylous seedlings. A, with aternary whorl of the firstleaves; B, with a leaf withtwo apices and a divided vein. level of the ground (e. however, numerous exceptions. In tricotylous cultures, dicotylous individuals some-times become ternary later. Thus I possess a plant withternary whorls of Aesculus Hippocastanuni (now 13years old), which only had two cotyledons, and fromthe same crop a plant which was tricotylous but has sinceproduced leaves on the decussate plan only. In ]:)Otlispecimens the change in the disposition of the leaves Tricotyly and the Amuigciiicfit of Leaves. 371 toDk place before the cotyledons were dead. \\\ Dipsaeiissyl-iesfris tors its, a race which is usually ricli in lernar\-in(h\ iduals, these are almost without exception decussatein early youth. On the boundary between the 2- and 3-merous whorls2!/2-nierous ones not infrequen
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