The Embryology of some Anomalous Dicotyledons. 
BY 
DAVID M. MOTTIER, 
Professor of Botany in Indiana University. 
With Plates XXVI and XXVII. 
Historical. 
W ITHIN the past few years, the discovery of an anomalous character 
in the embryo of some species of certain dicotyledonous families 
has stimulated interest in the question of the phylogeny of the Angio- 
sperms, especially as these anomalies have been regarded as throwing some 
light upon the origin of the two divisions of the higher seed plants. The 
several observers have approached the subject from two standpoints, some 
dealing with the development of the embryo, while others have devoted 
themselves to the study of the comparative anatomy of seedlings. Of 
the publications that have recently appeared, dealing with the embryo- 
logical evidence, that of Lyon (’01) was among the first. This observer has 
shown that Nelumbo lutea , one of the Nymphaeaceae, is fairly typical of 
the known anomalous dicotyledons. The development of the embryo is 
described under four stages, namely, the ‘spherical stage/ the ‘ mono- 
cotyledonous stage/ the ‘ dicotyledonous stage/ and the ‘ mature embryo/ 
The early development in Nelumbo results in a spherical embryo, 
consisting of several hundred cells. Growth now takes place such that 
a flattened or button-shaped mass of tissue results. From the distal side 
of this mass the plumule, or rather the apex of the stem, appears as a small 
protuberance, as does also the single primordium of the cotyledons, which 
arises as a crescent-shaped mound of tissue around the rear of the embryo, 
its wings (points of the crescent) extending forward even with the plumule. 
Judging from Lyon’s Fig. 8 (1. c.), it seems that, at this stage, the plumule 
lies between the points of the crescentic cotyledonary primordium, but later 
it becomes situated within the space enclosed by the crescent. This closes 
the monocotyledonous stage. The subsequent development, immediately 
following, results in the cotyledonary primordium becoming two-lobed 
through the localization of growth at two nearly opposite points. With 
the final development of the embryo, these two lobes grow into the two 
large cotyledons. The sinuses between the cotyledons are not of equal 
[Annals of Botany, Vol. XIX. No. LXXVI. October, 1905.] 
