Dispersal of Herbaceous Angiosperms . 565 
woody Metachlamydeae. A great majority of the woody Dicotyledons 
and an overwhelming proportion (1,281 genera out of 1,569) of the arbores- 
cent ones thus occur among the more primitive of the two grand divisions. 
The origin of herbs among the Monocotyledons presents a somewhat 
different problem. The weight of evidence at present available from all 
sources seems to indicate that Angiosperms are monophyletic, and that the 
Monocotyledons have arisen as offshoots from an ancient (and therefore 
presumably woody) dicotyledonous stock, probably as a direct aquatic 
herbaceous adaptation, through steps similar to those by which the aquatic 
Halorrhagaceae, for example, seem to have sprung from such a semi-woody 
form as Halorrhagis. It seems clear that the shrubby and arborescent 
Monocotyledons have been derived secondarily from herbaceous forms, and 
do not correspond to the primitive woody Dicotyledons. The development 
of monocotyledonous herbs, however, seems to have taken place very far 
back under much more equable climatic conditions than those obtaining 
over most of the earth at present, and therefore in response to a very 
different climatic environment from that which we shall attempt to show 
has been the cause for the origin of most herbaceous Dicotyledons. When 
conditions arrived very favourable for the development of terrestrial herba- 
ceous vegetation, these herbs, long an inconspicuous part of the flora, 
assumed a much more prominent position ; and especially in the form of 
grasses, sedges, and rushes became widely distributed in temperate regions. 
The present paper, however, deals particularly with the apparently much 
more recent origin of herbs among the Dicotyledons. 
IV. Evidence from Phytogeography. 
Finally, evidence as to the relative antiquity of herbs and woody plants 
may also be obtained from a study of the present distribution over the earth 
of the members of these two groups. The writers have with some care gone 
through a large number of published ‘ Floras 5 and lists of plants 1 from 
1 Analyses have been made of the following works : 
North America. — Vascular Plants of Ellesmereland, Simmons; Gray’s New Manual of 
Botany, Robinson and Fernald; Manual of the Flora of the Northern States and Canada, Britton; 
Flora of the South-Eastern United States, Small ; Flora of the Southern United States, Chapman ; 
Flora of the Florida Keys, Small ; Flora of the British West Indian Islands, Grisebach ; New 
Manual of Rocky Mountain Botany, Coulter and Nelson ; Flora of Los Angeles and Vicinity, 
Abrams. 
South America. — Flora Braziliensis, Martius, Eichler, and Urban ; Report on the Princeton 
Expedition to Patagonia : Botany, Macloskie. 
Europe.' — Islands Flora, Stefansson ; Botany of the Faroes, Warming and others; Handbog i 
Norges Flora, Blytt ; Flora Rossica, Ledebour ; Handbook of the British Flora, Bentham and 
Hooker; Flora des Nordostdeutschen Flachlands, Ascherson and Graebner; Flora der Schweiz, 
Schinz and Keller ; Flore fran^aise, Cusin and Ansberque ; Compendio de la Flora espanola, Ibiza ; 
Description physique de l’Ue de Crete : Botanique, Raulin ; Flora Sicula, Tornabene ; Flora of 
Syria, Palestine, and Sinai, Post ; Flora Orientalis, Boissier. 
Asia. — Index Plant arum Japonicarum, Matsumura ; Flora Hongkongiensis, Bentham; Flora 
Q q 2 
