820 
Compton. — An Anatomical Study of 
It has already been remarked that there is a close similarity between the 
structure of a seed-leaf produced by fusion and one undergoing fission. 
This opens the door to the view that dicotyly may have been derived from 
polycotyly by a series of fusions. It is only possible to decide between the 
opposing views on the basis of other classes of evidence and on comparative 
studies. 
The only recent argument in favour of a polycotylous origin of dicotyly 
in Gymnospermae is that brought forward by Coulter and Chamberlain , 1 
who remark that ‘ it must be remembered that probably our oldest group of 
Coniferales, older even than the Cycadales and Bennettitales with which we 
are acquainted, is the extreme illustration of polycotyledony, while the 
youngest of the Coniferales are dicotyledonous or nearly so’. With the 
implication of primitiveness in the word ‘oldest' I cannot agree, for the 
argument is founded on our ignorance and the imperfection of the geo- 
logical record : and almost the whole of modern morphological work tends 
to the conclusion that it is the dicotylous Podocarpeae and Araucarieae 
which must be regarded as the most primitive Coniferales ; the polycotylous 
Abietineae, old as they are, being a relatively advanced family. 
The earliest known embryo, that of Bennettites , was dicotylous ; the 
cotyledon-bearing Pteridophyte, Selaginella , is dicotylous ; and numerous 
lines of investigation have led to the conclusion that dicotyly is a primitive 
character — whether for the Monocotyledons, or for teratological syncotyls 
and schizocotyls, for polycotylous Proteaceae and Loranthaceae, or for 
Gymnospermae. 
Botany School, 
Cambridge. 
Bibliography. 
Cesalpini, A. (1583) : De plantis libri xvi. Florence. 
Chauveaud, G. (’ll): L’appareil conducteur des plantes vasculaires. Ann. Sci. Nat. (Bob), 9 e ser., 
t. xiii, p. 1 13. 
Compton, R. H. (’12 a ) : Theories of the Anatomical Transition from Root to Stem. New Phyt., 
xi,p. 13. 
— (T2 b ) : An Investigation of the Seedling Structure in the Leguminosae. Journ. 
Linn. Soc. (Bot.), xli, p. 1. 
Coulter, J. M., and Chamberlain, C. J. (TO) : Morphology of Gymnosperms. Chicago, p. 297. 
Dodel, A. (’72) : Der Uebergang des Dicotyledonen-Stengels in der Pfahlwurzel. Pringsh. Jahrb., 
viii, p. 149. 
Dorety, H. A. (TO) : In J. M. Coulter and C. J. Chamberlain, Morphology of Gymnosperms. 
Chicago, p. 427. 
Duchartre, P. (’48) : Sur les embryons dits polycotyles. Ann. Sci. Nat. (Bot.), 3 e ser., t. x, p. 207. 
1 Coulter and Chamberlain (TO), p. 300. See also Dorety (TO), p. 428. 
