IV. Anatomy of Teratological Seedlings. 
475 
ascribed to the conflicting internal tensions set up (Fig. 65). In some cases 
the transition features show no noteworthy variation from those of normal 
dicotyls (Fig. 66), but several show rather remarkable modifications, and some 
of the most clearly defined of these are described below. 
£ Seedling C 5 (Fig. 9) is an amphisyncotyl showing a salver-shaped 
condition. The marginals and laterals of both cotyledons on one flank 
unite with their respective midribs at a fairly high level, thus causing the 
latter to appear to have undergone displacement to one side (Fig. 67). The 
midribs themselves are mesarch and are almost enclosed by their phloems, 
which form strongly incurved arcs (Fig. 67). The bundle systems of the 
other side gradually unite until they form 
a large mesarch xylem mass, the phloems 
of which are linked locally with the 
adjacent half-phloems of the midribs 
(Fig. 68). This xylem mass loses its 
protoxylem and gradually becomes very 
much reduced, being represented at the 
base of the hypocotyl by a little meta- 
xylem only. The midribs alone con- 
tribute to the root-whorl, which thus 
consists of two members (Figs. 9, 69), 
and below these a protoxylem is de- 
veloped in the plane of the third hypo- 
cotyledonary xylem group, the tap-root 
being triarch. 
‘ Seedling D * (Figs. 10 a , 10 b ) is ex- 
ternally a seedling of similar type to 
the previous one, but its vascular ar- 
rangements are somewhat different. The 
midribs are well defined, as are the marginals of one side, but generally 
speaking the lateral systems of both cotyledons consist of an elaborate 
anastomosing series of small veins which may locally extend into the solid 
basal tissue formed by the secondary ingrowths from the adaxial petiolar 
surfaces. The well-defined marginals after a temporary union diverge, and 
the whole of the bundle complex gradually concentrates upon the two mid- 
ribs, uniting with these adaxially so that a pair of mesarch xylem groups, 
completely surrounded by phloem, enters the hypocotyl (Fig. 73). 
Traversing the hypocotyl the xylem becomes exarch and the sheaths of 
phloem open at the protoxylem (Fig. 74, b), so that for a time they are U- 
shaped in transverse section. A little lower down they divide into two 
parts which unite laterally, the xylems becomipg united at the same level, 
so that a diarch plate results (Fig. 74, c , d). Two lateral roots are given off 
at the base of the hypocotyl, and the tap-root is diarch. 
Figs. 64-66. An amphisyncotyl (Fig. 
] 1 ) in which partial roofing-in of the 
plumule has occurred, and in which the 
cortex shows splits due to tissue tensions. 
