79 
e 
and Clematideae, characterised by achenial 1-seeded carpels. 
It seems probable that apparent affinity between genera in the 
‘two groups is due to parallel evolution. Of the Helleboreae, for 
instance, the small apetalous-flowered genus Hnemion has some- 
times only one seed in its follicular fruit, obviously the result of re- 
duction and it approaches very closely some species of Thalictrum 
of the Ranunculeae. Apart from this degraded Enemion type of 
flower, however, the tribe Helleboreae appears to have developed 
very specialised types of inflorescence and flowers and to have 
produced in one direction the subtribe Cimicifuginae, in another 
the genus Aquilegia through Paraquilegia and Semiaquilegia, 
whence also the tribe Delphineae may also owe its origin, whilst 
Ranunculeae have culminated in the apetalous groups Anemoneae 
and Clematideae as already noted. 
It should be remarked that coincident with the reduction of 
one whorl of the perianth we have the singular aggregation of the 
upper leaves into a protective involucre so marked a feature of 
tribe Anemoneae, as if to compensate for the apetalous condition. 
Thus the involucre comes to function as an ordinary calyx, and 
is scarcely distinguishable from such in the genera Hepatica and 
- Barneoudia. With the assumption of the climbing shrubby 
habit in Clematis, wherein it was no longer required on account 
of this new mode of growth, the involucre seems to have been 
dispensed with. Its retention in some of the species of Clema- 
topsis, an intermediate genus, is noteworthy. 
The elongated carpellary axis of Myosurus, recalling as it does 
_ the cone-like structure of the more primitive Magnoliaceae, must, 
having regard to the saccate sepals, be looked upon as a primitive 
feature retained in or perhaps returned to this genus. In another 
direction, namely, in having broadly-winged seeds contained in 
two partially connate carpels, the genus Glaucidium departs 
markedly from the usual type of carpellary structure, the general 
habit of this plant suggesting affinity with Podophyllum in the 
Berberidaceae. ; 
GEOGRAPHICAL DISTRIBUTION OF RANUNCULACEAE. — 
_. Ranunculaceae are to be found in nearly every part of the 
globe. They are relatively most abundant, both in species and 
individuals, in the temperate regions of the Northern Hemisphere, — 
and are comparatively rare in the tropics, there found mainly 
on the mountains and high plateaux. 
In Lapland* the family represents about ,', of the total 
phanerogamic vegetation. The most widely spread species in 
* Lecoq, Geogr. Bot. 4: 404 (1855). 
