Cockayne, L. 1902 : A Short Account of the Plant-covering of Chatham Island. Transactions and Proceedings of the New Zealand Institute 34: 243-325.
Cockayne (T.N.Z.I. 33, 1901, 275) gives a full account of seedlings and young plants grown from the Chatham Id variety. He says: "The similarity of appearance in form between the seedlings and adult leaves . . . was pointed out to me . . . by Mr. S. D. Barker." He was advised by Mr. F. A. D. Cox that the Chatham Id plant "certainly does not pass through the stages you have mentioned; as far as I have observed branches and twigs are always upright, as in the mature form, and leaves always the same shape." Later (T.N.Z.I. 34, 1902, 319) he gives the name P. chathamicus sp. nov., with the remark: "I have separated this plant from P. betulinus because they differ in the seedling state, and P. chathamicus is also never furnished with reversion shoots."
NZOR Concept Id
NZFLORA (2012-) New Zealand Plant Names - Name based concepts