Anatomy of Ter at o logical Seedlings. IV. 473 
petioles is a common feature of normal seedlings and occurs in many of the 
abnormal seedlings also (Fig. 43). Occasionally, as in the seedling just 
described, the whole of the petiole is involved and leads to an asymmetrical 
amphisyncotyly. This condition may exceptionally cause a partial roofing- 
in of the plumular bud owing to secondary fusions of the apposed cotyle- 
donary tissues. The effect of this roofing-in is apparently in many cases to 
cause a partial arrest of plumular development, since, as a general rule, the 
plumule is ill developed compared with that of other seedlings of similar size 
and age in which the cotyledonary tube is rudimentary or absent. The seed- 
ling illustrated in Fig. 8 is a case in point. Both from the standpoint of size 
and the amount of secondary thickening present this seedling should have 
possessed a partially expanded epicotyl, but as a matter of fact it shows 
a stage of development very little in advance of that possessed by quite 
young seedlings. Its position is indicated by a large swelling in the basal 
portion of the tubular petiole, and some idea of the relatively enormous size 
of this region may be gleaned from a comparison of Fig. 60 with that of the 
same region in other seedlings. The cotyledonary tube communicates with 
the exterior only by a small pore (Fig. 6 and the adjoining tissues show 
evidences of compression in the rows of flattened cells which are indicated 
by dotted lines in the diagram. The vascular details of this seedling also 
serve to illustrate one or two points of interest. The midrib forms one 
xylem pole in the hypocotyl and the marginals constitute another, both 
laterals remaining independent and showing an endarch position of the 
protoxylem (Fig. 61). One of the independent laterals persists throughout 
the hypocotyl but loses its protoxylem, whilst the other soon dies out com- 
pletely, its position being represented for a short distance by a small patch 
of secondary xylem (Fig. 61). Towards the base of the hypocotyl a new 
bundle appears in the same relative position (Fig. 62), and though it does 
not give rise to a root at the root-whorl, which consists of three members, it 
is continued downwards and forms a root-pole. It will be noticed that the 
history of this particular root-pole is capable of two interpretations, since it 
may be derivable either from the independent lateral, which died out after 
a brief course in the upper part of the hypocotyl and has subsequently been 
restored, or it may be an entirely new structure. The second view seems 
the more probable, since in all other cases observed, with the exception of 
‘ Seedling A’, and of the syncotyl with unequal cotyledons previously described, 
where an independent lateral dies out in the upper hypocotyl, no root-pole of 
any kind is formed in the corresponding position. Hill and de Fraine ( 16 ) 
record a case in Pinus sylvestris in which there is a local disappearance of 
a vascular strand, and similar cases have been noted by other investigators ; 
but these are hardly comparable with the case under discussion, in which 
a distance of over three centimetres separates the termination of the one 
strand from the initiation of the other. Amphisyncotyly involving both 
