698 
Thomas . — Seedling Anatomy of 
in the plane joining the centres of the two cotyledons, which will be referred 
to as the cotyledonary plane . In rather less than one-third of the species 
chronicled (including those described in this paper) there are two other 
poles in the plane passing between the cotyledons — the intercotyledonary 
plane . 
(b) In a very few cases the poles of the tetrarch root lie in the diagonal 
planes. 
I shall refer to (a) as the Cruciform arrangement, of which there 
are the diarch and the tetrarch varieties, and to (b) as the Diagonal , of which 
there are at least the tetrarch and octarch varieties. 
The Cruciform type is accompanied by the peculiar vascular arrange- 
ment in the base of the cotyledons, which has been variously interpreted 
as one bundle or two, and to which the name of 4 double bundle ’ has been 
applied. 
The double bundle essentially consists of two groups of phloem, with 
one group of protoxylem placed between them. The three groups are 
always on different radii, so that M. Chauveaud 1 well describes the relative 
positions as 4 alterne While maintaining this general arrangement, the 
details of the strand at any one level are frequently characteristic of syste- 
matic groups of greater or less magnitude. The protoxylem groups are 
continuous with the poles of a diarch root, the xylem plate of which is. thus 
always formed in the planes passing through the centre of the cotyledons. 
When the primary root is tetrarch, the intercotyledonary poles are repre- 
sented in the cotyledons by groups of protoxylem, which may be found 
on the flanks of the ‘ double bundle * (see Althaea rosea , PI. LI, 
Figs. 23, 24, 25), or may be more or less detached from it as lateral 
strands (see Magnolia tripetala , PI. L, Figs. 9-12). 
The Diagonal type, judging from my own observations and from the 
published work of others, is far less common, and may indeed perhaps 
be regarded as rare. I have observed it in Calycanthaceae, P'agaceae, 
Euphorbiaceae, and it has been described by Miss W. Smith 2 in the 
Sapotaceae and by Mr. Wright 3 in the Ebenaceae. Its relation to the 
Cruciform type is not obvious, but there are some significant features which 
will be considered later. It may be combined with the Cruciform type to 
form an octarch root if four of these poles are present, or a hexarch root 
if only the cotyledonary poles of the cross be present (e. g. Pyrus com- 
munis , Sic.). It is usually accompanied by that wide separation of the 
halves of the ‘ double bundle ’, together with early obliteration of the central 
1 Loc. cit. 
2 Smith, W. : The Anatomy of some Sapotaceous Seedlings. Trans. Linn. Soc., ser. ii, Bot., 
vol. vii, 1909. 
3 Wright, H. : The Genus Diospyrus in Ceylon. Ann. Roy. Bot. Gard., Peradeniya, vol. ii, 
1904. 
