Note 40 — Chapter XII · CHANGES OF SHAPE OTHERWISE CAUSED.

Natural selection may have operated in establishing a constitutional tendency to other sudden abridgments. Mr. Tansley alleges that this is a part-cause of the varying distribution of leaves. He says:—“I have myself made some observations on the length of internodes in the Beech, and am satisfied that it follows quite other laws, connected with the suitable disposition of the leaves on the branch. Although I have not had the opportunity of following up this line of work so as in any way to generalize the results, I suspect that ‘indirect equilibration’ is a widespread cause of such variation.”