590 Davey . — Seedling Anatomy of certain Amentiferae. 
adjacent to the plane and the dying out of those remote from it. The stele 
becomes contracted and an endodermis is differentiated (Fig. 13). The cen- 
tral cotyledonary protoxylem reappears in the form of a few feebly lignified 
disorganizing elements. At lower levels similar protoxylem appears at the 
intercotyledonary poles. Near the collet the metaxylem makes contact 
with the protoxylem poles so that four somewhat extended xylem secants 
are formed, alternating with the phloem groups which have maintained their 
diagonal position. Below the collet the metaxylem becomes compacted 
and a tetrarch root stele results. 
The first plumular leaf-trace is double at the cotyledonary node, but is 
differentiated so slightly before secondary thickening ensues that it makes 
no connexion with the primary structure of the hypocotyl. The cambium 
at first develops in two bands, as in Alnns and Be tula. 
Corylus Avellana. This is a large seedling with fleshy hypogeal 
cotyledons and a very short hypocotyl as externally limited. There is 
early elongation on the part of the plumular axis, which bears rudimentary 
leaves, as in Juglans and Carya. 
The cotyledon petioles each contain two massive and rather widely 
separated strands which enter the axis diagonally, as in Carpinus . At the 
cotyledonary node a small group of protoxylem is present between these 
strands, and can be traced downwards in the cotyledonary plane throughout 
the hypocotyl. The four groups of metaxylem from the cotyledons become 
each divided into two, and the resulting portions approach the neighbour- 
ing cotyledonary or intercotyledonary planes. Root poles are organized 
in the cotyledonary plane, as in Carpinus. In the intercotyledonary plane 
there persist the traces of the first and second plumular leaves. Their 
phloem in each case consists of two groups which diverge and unite with 
that of the cotyledons, while their xylem forms arcs of small scattered 
elements linking the adjacent cotyledonary metaxylems. Extended xylem 
secants consisting of plumular and cotyledonary elements are thus formed, 
and become compacted at lower levels into the intercotyledonary xylem 
poles of the cruciform tetrarch root. The replacement of tangential by 
centripetal development of the xylem takes place so gradually that typical 
root-structure is attained only at some distance below the collet. 
In this seedling the intercotyledonary root poles are connected partly 
with the cotyledon traces and partly with those of plumular leaves, thus re- 
calling Juglans Sieboldiana. The plumular portion is not so well marked 
as in the latter species, and is continued into the epicotyl as a double strand 
without central protoxylem. 
Fagaceae. With the exception of Fagus sylvatica , the members of 
this family to be described possess large hypogeal seedlings in which the 
early plumular leaves are rudimentary. In all the species the cotyledon 
blades are prolonged downwards below their junction with the petioles. 
