588 Davey.— Seedling Anatomy of certain Amentiferae . 
described, but the central cotyledonary protoxylem may be feebly de- 
veloped. Neighbouring phloems unite in the intercotyledonary plane 
at a high level. In descending the hypocotyl the central cotyledonary 
protoxylem gradually dies out, while the metaxylem becomes extended, and 
exarch protoxylem groups appear in contact with it at the diagonal corners 
cot. 
intercot. 
Figs. 9, 10, 11. A Inns cor difolia. 9. Trans- 
verse section of hypocotyl near cotyledonary node. 
10. Transverse section of same at lower level, 
showing indications of six protoxylem centres. 
11. Transverse section of same at level of ‘collet’, 
showing diagonal tetrarch root. ph. = phloem ; 
px . = protoxylem ; cot. and inter cot. indicate direc- 
tions of cotyledonary and intercotyledonary planes, 
respectively. All x 360. 
of the stele (Fig. 9). For a time six protoxylem centres may be 
present, but the original cotyledonary groups cease to be differentiated, 
while those diagonally placed persist into the root. In the region marked 
by the external collet, phloem is differentiated in the cotyledonary plane ; 
thus completing a tetrarch root stele (Fig. ix). This method of forma- 
tion of a diagonal tetrarch root recalls what is described by Chauveaud 1 
1 loc. cit., p. 320. 
