Root-structure in the Hypocotyl. 105 
nearly the whole of the hypocotyl posseses a central cylinder of 
typical root-structure. In this type the change from stem-orientation 
to root-orientation of the vascular elements may take place wholly 
or partly before the cotyledonary traces have run together to form 
the stele of the hypocotyledonary axis. It is very common for a 
considerable portion of this change to occur in the actual bases of 
the cotyledons, and though its completion is in some cases more or 
less delayed, the cotyledonary node itself invariably shews the 
alteration in orientation already begun. 
The facts are referred to as transition-phenomena as a matter of 
descriptive convenience, but this designation in no wise involves an 
expression of opinion as to the morphological value of the cotyledon- 
traces which have been very variously interpreted. It should 
for instance be mentioned that the interpretation of the vascular 
structure of the cotyledonary node arrived at by Sterckx, 1 in accor¬ 
dance with the views of Gravis, an interpretation which supposes 
that we have to do with a contact between cotyledonary bundles and 
root-stele, is entirely at variance with the language used in the des¬ 
cription of this type given above. But this circumstance does not 
affect the fact that Sterckx’s paper contains a particularly full and 
well-illustrated account of the case in which the “ contact ” or 
transition occurs in the cotyledonary node. 
This type has been clearly described and figured by Gerard 2 in 
a number of forms, e.g. Nigella damascena, Argemone grandiflora, 
Fninaria grandijlora, Raphanns niger , Reseda alba , and by Sterckx 3 
in various Ranunculaceae. It has also been mentioned by one of 
us 4 as characteristic of Ranunculaceae, and again described by Miss 
Sargant 5 in Delphinium, Nigella and Anemone coronaria. 
We have found this type in fourteen genera of Ranunculaceae, 
in certain Berberidaceae, and in every genus examined (twenty-four 
in all) belonging to the orders Papaveraceae (including Fumariaceae), 
Capparidaceae, Resedaceae and Cruciferae, together forming the 
cohort Rhoeadales of Engler. 
The structure in question of course undergoes a certain amount 
of modification when traced through this wide range of forms. 
1 Sterckx. Reclierclies anatomiquessur l’embryon et les plan- 
tules dans la famille des Renoiiculacees. Mem. Soc. i;oj r . 
Sci., Liege, ser. 3, t. 2, 1S99. 
2 Gerard. Reclierclies surle passage delaracine alatige. Ann. 
Sci. Nat. Hot., ser. 6, t. 2, 1881. 
3 I.oc. cit. 
4 Tansley. Reduction in Descent. New Piiytoj.ogist, Vol. 
I., p- 132, 1902. 
5 Sargant. A Theory of the Origin of Monocotyledons founded 
on the structure of their seedlings. Ann. of hot, Vol. 17, 
Jan., 1903, p. 53, et seq. Diagram IX, 
