126 de Frciine .— The Seedling Structure of certain Cactaceae. 
The present communication forms part of Mr. T. G. Hill’s scheme of 
investigation of seedling-structure, and has been carried out with a view to 
discovering whether there is any relation between the external morphology 
of the seedlings and their anatomy ; in other words, whether the adult 
adaptations to physiological conditions, which have impressed themselves 
on the form of the young seedling, have had a corresponding influence on 
its internal structure. 
The forms of many of the seedling Cactaceae have been figured at 
various times, but as Ganong 1 has already given a full account of the work 
done in this direction no detailed reference is required here ; so far as has 
been ascertained; however, no observations on the seedling structure of 
any member of the family have been recorded. 
No details of the colour factors of the seedlings will be given, as this 
question also has been fully dealt with by Ganong. 1 Owing to the great 
difficulty experienced in obtaining seeds, and the failure of these in many 
cases, when procured, to germinate, it has been found impossible to examine 
representatives of all the genera; in all, forty-seven species belonging to 
eleven genera have been investigated. I wish, in this connexion, to express 
my thanks to Professor Trelease of the St. Louis Botanic Gardens and to 
Dr. Rose of the Smithsonian Institute, both of whom sent me seeds, 
and also to Mr. Hales, Curator of the Old Physic Gardens, Chelsea, 
who not only obtained many seeds for me, but kindly undertook the 
germination of them all. 
I should also like to take this opportunity of ex¬ 
pressing my thanks to Mr. T. G. Hill, at whose suggestion 
this investigation was begun, for the encouragement and 
advice which he has constantly given me throughout its 
progress. 
The methods employed were a slight modification of 
those described for the Gymnosperm seedlings; 2 in all 
cases the seedlings used were microtomed, and longi¬ 
tudinal preparations were frequently made in addition to 
the transverse series. 
The Seedling Structure of the Cactaceae. 
Pereskia. 
Pereskia n. sp Rose. The seedlings are of an ordinary 
dicotyledonous type and show no sign of succulence; they 
Fig. i. Pereskia have a long slender hypocotyl and two thin leaf-like coty¬ 
ledons, one very much smaller than the other (Fig. i). 
This asymmetry of the seedling, caused by the difference in size of its 
1 Ganong, W. F. : loc. cit. 
2 Hill, T. G., and de Fraine, E. : On the Seedling Structure of Gymnosperms, I. Ann. Bot., 
xxii, 1908. 
