78 Sargant . — Theory of the Origin of Monocotyledons 
an upright much shortened subterranean axis in which the 
first internodes of the stem, as well as the hypocotyl, are 
suppressed. The species of Anemone and Oxalis with united 
cotyledons are distinguished from their neighbours within 
those genera by their tuberous habit. 
M. Sterckx remarks that among the Ranunculaceae the 
species with concrescent cotyledons have short subterranean 
hypocotyls which are generally tuberous ( 38 , pp. 80, 81). The 
explanation he gives is that the united petioles of the cotyle- 
dons carry their blades upwards, and thus replace the elongated 
aerial hypocotyls of allied species. Lord Avebury gives a 
similar reason for the correlation of a tuberous hypocotyl with 
concrescent cotyledons among the Umbelliferae (Lubbock, 30, 
1 1 , pp. 23, 24). Darwin speaking of several pseudo-monocotyle- 
dons, together with some other species in which both cotyledons 
are very much reduced in size or even absent altogether, says : 
‘ From the several cases now given, which refer to widely 
different plants, we may infer that there is some close connexion 
between the reduced size of one or both cotyledons and the 
formation by the enlargement of the hypocotyl or of the 
radicle of a so-called bulb.’ He attributes this to correlation 
of growth : the expenditure of material in the formation of 
a bulb or tuber is balanced by the economy effected in the 
reduction of cotyledonary tissue (10, p. 97). 
The pseudo-monocotyledons of Table II are in fact also 
characterized by the early formation of tubers, or at least by 
the development of a much shortened squat axis. 
The formation of underground root-stocks, of tubers, corms, 
and bulbs, is characteristic of the plants called ‘ geophilous 5 by 
Professor Areschoug ( 3 ). The general definition of the term 
which he gives on page 1 is very wide : 4 We include under 
that head such plants as form the buds by which they re- 
produce the shoot underground : those plants in fact which 
develop their aerial organs more or less completely beneath 
the surface of the soil.’ Defined in this way the term would 
include all biennials and herbaceous perennials of the temperate 
and arctic zones, for the aerial shoots of all such plants dis- 
