74 
James Small. 
who has shown that two New Zealand species of Senecio, S. 
saxifragoides and 5. lagopus, are microspecies of the same 
aggregate. They are distinguished only by the sparseness or 
abundance of the bristle-like, glandular hairs on the leaves. 
Those differences in degree, being certainly hereditary, con¬ 
stitute true unit characters.” It is further suggested that the 
difference is “of climatic origin” and that “ the drier climate of 
the Port Hills has directly determined the development of 
5. saxifragoides .” 
Other papers of interest in connection with epharmosis are 
by Harshberger (X, 35), Raunkiaer (43), Poole (42), Bonnier (X, 
8-9), Cockayne and Foweraker (X, 17), Dauphine (X, 22), 
Foweraker (X, 26), Gates (X, 27), Harris (X, 33), Oger (X, 56), 
Schroter and Hauri (X, 60), Shreve (X, 63-64), Sinnott and 
Bailey (46 and X, 5), Massart (X, 53), and Eames (15). For 
further literature the reader is referred to Goebel (19), Warming 
(X, 71), Henslovv (X, 38), Cockayne (X, 15-17), Schimper (IX 
32) and De Vries (IV, 87, pp. 438 seq.). 
Isolation and Differentiation. 
A. Jordan’s theory of the origin of species by isolation was 
revived by D. S. Jordan (X, 45) and is expressed thus. “Given 
any species in any region, the nearest related species is not 
likely to be found in the same region nor in a remote region, 
but in a neighbouring district separated from the first by a 
barrier of some sort.” This is shown to be true for Eriodictyon 
by Abrams and Smiley (X, 1) and the idea is applied by some 
taxonomists, when they raise geographical forms to specific rank 
(cp. 37). It is not, however, recognised as a general truth in 
the plant kingdom, for as Lloyd (X, 47) points out, the more 
general phenomenon is the occurrence of the most closely 
related species in the same region. Cockayne (X, 15) gives a 
number of specific instances of the occurrence of closely related 
species side by side in the same region and quotes Leavitt (34), 
who considers this phenomenon to be evidence in support of the 
action of mutation rather than that of natural selection or 
epharmosis. “ Mutation breaks the species, and momentarily at 
least must give a polytypic aspect to the group within a specific 
area ” ( loc. cit. p. 211). 
The thedry of “ the diffentiation of primitive world-ranging 
types in response to the differentiation of their conditions ” 
(Guppy, IX, 22, p. 313) has already been mentioned (Chap. X, A) 
