676 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



" But there is no sound basis for the assumption that the 



Dicotyledons are derived from Monocotyledons ; indeed the palaeontological 

 evidence seems to point to the Dicotyledons being the older. This, how- 

 ever, does not entitle us to assume the origin of Monocotyledons from the 

 Dicotyledons, though there is manifestly a temptation to connect the 

 bilobic forms of the former with the ranal ones of the latter." 



Miss Sargent believes that the single cotyledon of Monocotyledons was 

 derived from both the cotyledons of a remote ancestor, and strong evidence 

 in favour of this view is given by her paper. 



In an abstract there is danger of interference with the proportions of 

 an argument, but it must be mentioned that a table is given of " Dicotyle- 

 donous seedlings with a well-marked cotyledonary tube " (familiar in 

 Delphinium And Anemone), and another of "Pseudo-monocotyledons," a 

 familiar example of which we have in Cyclamen. An interesting part of 

 the paper is that on the origin of the Monocotyledonous habit. " Comparison 

 of the species mentioned in Table L (the first above quoted) with each 

 other shows that they have another character in common besides that of 

 a cotyledonary tube. With one exception their hypocotyl is always much 

 reduced in length and is commonly thickened . . . The great majority of 

 the species mentioned are tuberous ; and others (Podophyllum, Serratula, 

 Polygonum, Rheum) form 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 . . . Darwin, speaking of several pseudo-monocotyledons, 

 together with some other species in which both cotyledons are very much 

 reduced in size, or absent altogether, says : ' From the several cases now 

 given, which refer to widely different plants, we may infer that there is 

 some close connection 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 expendi- 

 ture of material in the formation of a bulb or tuber is balanced by the 

 economy affected in the reduction of cotyledonary tissue . . . Concrescent 

 cotyledons seem to be an adaptation for producing effective assimilating 

 surfaces with the least possible expenditure of material. The production 

 of a single cotyledon, whether by the more complete fusion of two or in 

 any other way, is also an economy as compared with the formation of two 

 cotyledons. It is true that in time the extra assimilating surfaces will 

 more than repay the cost of their production, but time may fail the geo- 

 phyte which dares not risk being caught by the bad weather unprepared. 

 These considerations have led me to look upon the Monocotyledon as an 

 organism adapted primarily to a geophilous habit. The single cotyledon 

 has been shown to be connected with this way of life in some Dicotyledons, 

 and many of the features which distinguish Monocotyledons from Di- 

 cotyledons may be explained as having been formed by the conditions 1 

 have just described. Since I have adopted this view as a working hypo- 

 thesis, the purpose of many details in the structure of Monocotyledons, 

 which had puzzled me before, has become comprehensible." This paper 

 is largely anatomical, and, in spite of the importance of such details, they 

 must here be passed over. Various points of interest arise all through. 



