492 Willis. — Plant Invasions of New Zealand . 
invasions of New Zealand were probably four — northern, Kermadec, 
western, and southern — the western probably arriving by the ridge on which 
stand Norfolk and Lord Howe. 
Applying the usual method of prediction and verification, it is then 
shown that (i) a large part of the floras of these islands also occurs in New 
Zealand ; (2), (3), and (4), genera and families not represented in New 
Zealand by actual species, are represented by endemics or by Australian 
and Polynesian wides in the islands ; (5) more than half the species not 
found in New Zealand are endemic to the islands, and (6) the rest are 
Australian and Polynesian wides ; (7) these species belong very largely to 
genera and families that do reach New Zealand ; (8) families and genera 
that have reached New Zealand are better represented on the islands than 
those that have not ; (9) the families that do not reach New Zealand at all 
are all small and little distributed in the islands ; (10) the genera that do 
not reach New Zealand belong mainly to families that do ; (11) the bulk of 
the island floras belongs to genera and families of the northern, Kermadec, 
and western invasions of New Zealand; (12) the island endemics occur 
chiefly in genera and families that have reached New Zealand ; they occur 
chiefly in (13) the larger families of the islands, and (14) the larger genera; 
(15) the island genera with endemics are usually large in New Zealand ; 
(16 and 17) the island families and genera with endemics are in general the 
same as in New Zealand; (18) the island endemics belong chiefly to the 
families that reach three islands; (19) the largest families in the islands are 
those reaching all three, and (20) similarly the largest genera ; (21) the 
families that reach three are best represented in New Zealand, and (22) simi- 
larly the genera ; (23) the species in common between three islands show the 
largest proportion of wides, then those from two and from one. 
Literature. 
1 . Arber : On the Law cf Age and Area, in relation to the Extinction of Species. Ann. of Rot., 
xxxiii, 1919, p. 2ir. 
2 . Cheeseman : Flora of New Zealand. Wellington, 1906. 
3 . Hemsley : Flora of Lord Howe Island. Ann. of Rot., x, 1896, p. 221. 
4 . Maiden : Flora of Norfolk Island. Journ. Linn. Soc., N.S.W., xxviii, 1903, p. 692. 
5 . Oliver : Vegetation and Flora of Lord Howe Island. Trans, and Proc. N.Z. Inst., xlix, 
1917, p. 94. 
6. SlNNOTT: The Age and Area Hypothesis, &c. Ann. of Rot., xxxi, 1917, p. 209. 
7 . Willis: On Ceylon. Phil. Trans., R., ccvi, 1915, p. 307; Proc. Roy. Soc., B., lxxxix, 1916; 
and Ann. of Rot. xxx, 1916, p. 1. 
8. : On New Zealand, eight papers in Ann. of Rot., 1916-19, especially— 
9 . : Distribution of Species in N.Z., xxx, 1916, p. 437. 
10 . — : Sources and Distribution of the N.Z. Flora, xxxii, 1918, p. 339. 
11 . — : Floras of the Outlying Islands . . ., xxxiii, 1919, p. 267. 
