7*4 
Thomas. — Seedling Anatomy of 
Berberis and Laurus form a tetrarch root in the absence of laterals (Text-fig. 
25, 2). Calycanthus presents that wide separation of the halves of the double 
bundle with almost complete obliteration of the central protoxylem which 
is one of the most puzzling aspects of seedling anatomy, and it is coupled 
with two forms of root. 
Rhoeadales. 
About thirty species have been examined belonging to the Rhoeadales 
cohort. They show very great constancy of feature and present good 
typical examples of the diarch type. They include members of the 
Cruciferae, Papaveraceae, Resedaceae, and Capparidaceae. They are for 
the most part herbaceous forms, but the shrubby Capparis and Cleome are 
very similar in their anatomy. The species here described include Papaver , 
instanced by de Bary 1 as a form with one bundle to the cotyledonary trace, 
and Cheiranthus , stated by Scott 2 to have two. Corydalis and Fumaria , in 
common with the other members of the group, present the features which 
have been described by all recent authors as illustrative of Van Tieghem’s 
Type 3, but Van Tieghem 3 himself gives Fumaria as an example of 
Type 1. 
Cruciferae. 
This order shows very uniform structure and it is only in the neighbour- 
hood of Lunar ia that there is any departure from type. 
Hesperideae. 
Cheiranthus Cheiri. The hypocotyl shows a somewhat elliptical 
vascular cylinder consisting of the usual diagonal strands of phloem and 
metaxylem. The pairs at each end of the ellipse are connected by the 
more or less crushed protoxylem of the cotyledonary plane. Near the 
cotyledonary node the ellipse widens out and the vascular tissue at each 
end is continued into the cotyledons as the double bundles of the petioles, 
while the tissue in the intercotyledonary plane ultimately connects with 
the vascular system of the first plumular leaves. Proceeding towards the 
collet, the hypocotyledonary tissues become continuous with those of 
a diarch root (similar to that shown in PI. LI, P"ig. 16) by the following 
stages : (1) disappearance of the pith, (2) aggregation of the alternate 
phloem masses, and (3) reduction of the xylem to a single file of elements 
constituting the diarch plate. The epidermis and endodermis also change 
in character, but usually at a lower level. In the upper part of the 
cotyledon the double bundle is continued by a single strand. This is the 
now familiar diarch type (PI. LI, Figs. 17-20). The examination of a form 
with three cotyledons revealed a triarch root. 
1 de Bary, A. : Comparative Anatomy of the Phanerogams and Ferns, p. 236, (Oxford) 1884. 
2 Loc. cit. 3 Loc. cit. , p. 782. 
