312 Lee. — Observations on the 
possessing linear seed-leaves which unite at the base to form a very short 
cotyledonary tube. 
In each seed-leaf there are three principal strands present, the two 
laterals fusing with their fellows in the upper part of the hypocotyl 
(Diagram 6, 1, n). The fused bundles immediately pass inwards, but remain 
at some distance from the centre throughout the hypocotyl. The larger 
midrib strands undergo slight rearrangement, the protoxylem becoming 
exarch, but the phloem remaining more or less in position. Near the base 
of the hypocotyl, the four midrib strands approach nearer the centre, and 
the xylem elements (the number of which fluctuates) now become loosely 
Diagram 6. Leptosyne Douglasii. 
arranged and tend to intermix. At this level (Diagram 6 , III), though the 
structure simulates a tetrarch arrangement, it does not form an ordinary 
tetrarch root. The xylem is four-angled, but the angles consist, on the 
whole, of larger elements than the rest, although all the lignified tracheides 
and vessels are spirally thickened. In addition the phloem groups are 
situated outside and not between the angles. This condition obtains 
not only in the greater part of the hypocotyl, but also nearly to the 
root-tip. Finally, a gradual rearrangement occurs : some of the lignified 
elements disappear and the rest become more closely arranged to form 
a regular triarch root. Similarly with the phloem, three groups being 
formed which take up positions between the xylem angles (Diagram 6 , iv, v). 
