336 
Holden. — Observations on the 
A subsidiary line of evolution is exhibited by three seedlings in which 
a very complete cotyledonary tube is formed. Two of these show no special 
departure from the group as a whole in their vascular arrangements, but the 
third specimen is unique. In it there is no line of demarcation between 
cotyledonary petiole and hypocotyl, and the former consists of a more or 
less peltate basin-shaped structure, the floor of which is thrown into a number 
of wrinkles surrounding what looks like a small median pore (Figs. J a, 7 b). 
The vascular supply consists of the usual median, lateral, and marginal 
strands, but the two latter unite well inside the lamina, the resultant com- 
pound strands also fusing and becoming exarch very rapidly (Fig. 91). As 
a result the vascular system consists, immediately below the lamina, of two 
Figs. 91-96. Anomalous Group II seedling with peltate cotyledon 
(Fig. 7), showing abnormal bundle behaviour. 
bundles, the one derived from the laterals showing for a time the curious 
pseudoconcentric structure to which reference has been made in the other 
seedlings (Fig. 92). During their passage down the hypocotyl their 
behaviour is somewhat anomalous, that from the median strand remaining 
endarch, and turning outwards through 90°, whilst its exarch fellow also 
turns outwards through 90° to the same side (Fig. 93). The latter then 
swings back through 1 8o°, whilst the endarch bundle becomes mesarch and 
finally exarch and in so doing comes to occupy its normal position. The 
result is that the two lateral roots representing the root whorl lie at right 
angles to each other (Figs. 94, 95), and it is not until these have been given 
off that the normal diarch plate is evident. At no stage is there any 
evidence, apart from the pore in the floor of the lamina, of the median 
cavity which the epicotyl would occupy. This may be due either to 
occlusion by the ingrowth of the walls of the tube, or possibly to the 
suppression of the petiole, a view which is supported by the early union of 
