490 
Holden and Daniels. — Observations on the 
It finally remains to state the conclusions to which our investigations 
have brought us. Briefly we consider that, whilst in the present state of 
knowledge dogmatism as to the origin of monocotyledony would be most 
unwise, the view that it is the result of unilateral syncotyly has much to 
recommend it. It is not claimed that it is necessarily the sole method 
by which the monocotyledonous condition may have been attained, but it is 
held that it provides a consistent explanation of the observed facts in 
Monocotyledons proper and that it is one the evolution of which is well 
illustrated by both normal and teratological Pseudo-Monocotyledons. 
Summary. 
1. Impatiens Roylei produces two main types of abnormal seedling, 
one of which is obviously syncotylous (Type i) and the other, judged by 
morphological standards, heterocotylous (Type 2). 
2. The apparently heterocotylous type is in all probability the product 
of extremely close syncotyly. 
3. This conclusion is supported by the following facts : 
(a) Undoubted syncotyls occur in which the midrib bundles unite 
and behave in transition in a manner indistinguishable from that of 
a single normal midrib. 
(b) Syncotyls occur in which there is a progressively closer fusion 
of the originally separate cotyledonary axillary buds. 
(c) ‘ Type 2 5 seedlings occur in which the double origin of the bud 
is evident. 
(d) The modifications found in the epicotyl are very similar in 
both types of seedling. 
(e) The modification of the existing vascular components and 
the introduction of new vascular strands are fundamentally the same 
in both. 
4. The production of new vascular strands or the modification of 
existing ones is believed to be a reaction against the elimination of certain 
strands on the symphysis side, and to be explicable on physiological 
grounds. 
5. Amphisyncotylous seedlings occur, and these show in many cases 
a retardation in the development of the plumular bud which is held to be 
due to the partial roofing-in of this structure by the secondary tissue 
fusions occurring between the adaxial cotyledonary surfaces. 
6. Many amphisyncotyls show vascular modifications which appear to 
be related to their morphological conditions. 
7. The anatomy of a tricotyl and of an amphitrisyncotyl is also 
described. 
8. It is considered that the evidence submitted as to the origin of the 
‘ Type 2 * seedlings of I. Roylei , combined with that derived from the studies 
