204 MR. A. W- HILL--EREVISION OF 
of, and the lamina is seen to consist of a great number of tiny lobule. An opposite 
tendency in the direction of reduction must, however, also be noted, for in one species, 
N. elandestina (a native of the Atacama desert), a simple leaf-lamina appears to have 
been derived from the palmate type owing to the suppression of the lateral lobes *. 
The ternate type of leaf found in a few species (e. g. in N. aretioides, N. artemisioides, 
&c.) may also be considered as reduced from the 5-lobed leaf by the suppression of the 
external pair of lobes, since in rare cases traces of the lost pair of lobes may be found. 
It has been found possible to separate the various species into groups mainly on the 
type of the leaf-lamina and in this direction several tendencies in the mode of lobation 
of the lamina have been noted. In some species the lobing is only carried to the middle 
of the lamina, whilst in others the lamina is cut almost to the base, and this latter 
tendency culminates in those forms in which the leaf-lamina is dissected into a large 
number of linear segments, e. g. N. pedatiloba, N. sajamensis (Pl. 28, fig. 12). 
The various species falling into these groups can be further differentiated owing to the 
fact that the middle lobe of the leaf may remain comparatively simple or else may be 
lobed or subdivided in the same manner as the lateral lobes. 
The question of the behaviour of the median lobe introduces the consideration of the 
bipinnatifid group, in which a large number of species, and more particularly those which 
occur in the southern part of the range of the genus, are included. 
Owing to the strong development of the median lobe of a 5-lobed leaf accompanied 
by deep cutting and lobation of the segments, it appears that a palmatilobed type of 
leaf with more or less pinnatifid segments like that of JN. argyllioides may have 
arisen (cf. Pl. 27. figs. 6, 7). A deeply palmatifid type of leaf with similar and equal 
segments may have developed in the first place, and then, owing to the gradual increase 
in size of the median lobe, all stages in the evolution of a well-marked bipinnatifid leaf 
may have taken place. With the further development of the median lobe and its 
lateral segments or pinnæ, the most advanced type of bipinnatifid leaf is reached, In 
such cases, which are well illustrated by N. anthemidifolia and allied species, the 
origina] lateral lobes appear to be but little more developed than the segments of the 
highly developed median lobe (cf. Pl. 27. fig. 8). It is worth while in passing to call 
attention to a possible analogy, in the relation of the palmate tothe pinnate types of 
leaf, between the species of this genus and of the fan and fern-leaved varieties of the 
Chinese Primula, P. sinensis, since the fern-leaved type appears to be a definite sport 
from the fan-leaved type, due, as it seems, to the vigorous development of the median 
lobe. It may be, then, that the palmate and pinnate forms of Nototriche owe their origin 
to an original tendency in an ancestral type to produce offspring with either a palmate 
or pinnate form of leaf, and from this tendency has resulted the extraordinary diversity 
of leaf-form to be found in this genus. 
Since two or three species of very different leaf-type may be found growing close to 
one another under exactly similar conditions, it does not appear that one particular form 
of leaf is better adapted than another to any definite and given set of conditions. 
Tomentum.—The distribution and character of the hairs on the lamina and petiole are 
* Cf. the apparently simple leaves of Berberis vulgaris, Robinia monophylla, &c. 
