The Seedling Structure of certain Cactaceae. 
BY 
ETHEL DE FRAINE, B.Sc., F.L.S., 
University of London, Goldsmiths 11 College. 
With eighteen Diagrams and nineteen Figures in the Text. 
/CONSIDERABLE importance has of late been attached by some ob¬ 
servers 1 to the transition-phenomena in seedlings of Spermophyta, 
more especially with regard to the help given by them in the elucidation of 
phylogenetic problems. In view of the value thus assigned to seedling 
anatomy it seemed desirable to make as complete a study as possible of 
the seedlings of some well-defined families. The Cactaceae, with their 
marked adaptations to dry conditions, seemed to offer a profitable field for 
investigation, particularly as the form of the seedlings of this group bears 
so evident a relation to that characteristic of the adult. 
Ganong, 2 in his comprehensive account of the morphology of Cactaceous 
seedlings, states that the progressive condensation of the embryos runs 
strictly parallel to the condensation in the adults—it has its lowest term in 
Pereskia, and reaches its highest in the almost globular Mamillarias ; further, 
this condensation is due to adaptation to a habitat of increasing desert 
conditions. He suggests that the form of the adults, ‘ as it becomes more 
and more fixed and intensified, tends to work back into earlier and earlier 
stages in the ontogeny of the successive individuals; until, finally, a character 
adaptively acquired by the adults works back into the epicotyl . . . and 
finally into the embryo.’ This ‘ working back into the epicotyl ’ may be 
comparatively rapid, but the impression of such features on the embryo 
seems very slow ; this is ‘ due no doubt to the fact that the embryos have 
a set of activities of their own in their early life which keeps them from 
being too plastic to other influences working upon them ’. 
1 Sargant, E. : Theory of the origin of Monocotyledons, founded on the structure of their 
seedlings. Ann. Bot., xvii, 1903. 
Tansley, A. G., and Thomas, E. N.: The Phylogenetic Value of the Vascular Structure of 
Spermophytic Hypocotyls. Report of Brit. Ass., Section K, 1906, p. 761. 
2 Ganong, W. F. : Contributions to a Knowledge of the Morphology and Ecology of the 
Cactaceae. II. The Comparative Morphology of the Embryos and Seedlings. Ann. Bot., xii, 1898. 
[Annals of Botany, Vol. XXIV. No. XCIII. January, 1910.] 
