196 
Hill and de Frame . — On the 
Picea ajanensis. The seed-leaves vary in number from six to nine, for 
the genus Masters 1 states that the number of cotyledons is five to fifteen. 
Series A. Six cotyledons. The endarch collateral bundles move 
towards the centre of the axis, and are arranged in three pairs (Diagram 3, 
Fig. 1, a. b., c. d., and e.f), alternating with the three plumular traces derived 
from the foliage leaves from the first whorl (/. i,p. 2,/. 3). The centri- 
petal displacement continues so that the individuals of each pair of 
cotyledonary strands become contiguous ; finally a complete vascular ring 
is formed. At a lower level the protoxylems of each pair of bundles rotate 
towards each other, the metaxylem, in two cases out of three, still being in 
continuity, and the phloem still forming a practically uninterrupted ring 
(Diagram 3, Fig. 2). This rotation of the xylem before the phloem and 
metaxylem has split is somewhat unusual, although it does sometimes occur 
in Tsnga canadensis . Then the original pairs of seed-leaf-traces separate 
so as to leave the protoxylem exposed and, at the same time, the fusion 
1 . 2 . 5 . 
Diagram 3. Picea ajanensis. 
of the plumular bundles with the strands of the seed-leaves becomes so 
intimate that it is no longer possible to delimit their boundaries. There 
thus results three phloem masses with much metaxylem on their inner 
sides alternating with three groups of protoxylem elements (Diagram 3, 
Fig. 3). The completion of the rearrangement results in a triarch root- 
structure. From these facts it is clear that each seed-leaf represents 
a half-cotyledon. 
Series B. Seven cotyledons. The transition was effected as in 
Series A, but instead of there being three pairs of cotyledon-traces, there 
were two pairs and a group of three. The root as before was triarch. The 
behaviour of the seed-leaf-strands showed that one cotyledon was subsidiary 
and the rest were half-cotyledons. 
Series C. This seedling was very much younger than the rest and had 
eight seed-leaves, of which two were subsidiary and six were half-cotyledons. 
A triarch root was formed. 
1 Masters, loc. cit. 
