91 
Teratologiccil Seedlings , It. 
examined show a behaviour strictly comparable with that found in Cheir - 
anthns Cheiri , examples of type a and type f$ being abundant, and in so 
far as this is the case the conclusions previously drawn are confirmed. 
There are, however, in some respects interesting points of difference between 
the two forms. 
An examination of the material shows that there is in CentranthnS 
a tendency towards the fusion of distinct parts, this showing itself in the 
attempts at the formation of a cotyledonary tube, in the existence of the 
di- and tri-syncotyls, and in numerous fusions, partial or more complete, of 
the cotyledon laminae among several groups of the polycotyls. Thus in 
hemitetracotyl C it seems highly probable that the bifid cotyledon has been 
produced as a result of a process of secondary fusion between two distinct 
cotyledons. The same feature is observable in hemitetracotyl D, and in 
many of the hemitricotylous seedlings, in which, as has been previously 
noted, there is frequently no relation between the level of fusion of the 
cotyledon halves and the level of union of the vascular bundles, so that the 
bundles may be distinct throughout the cotyledon, whilst there is only 
a slight apical notch visible in the lamina. 
A similar interpretation may be placed upon the instances in which 
hemitricotylous forms show triarchy persistent for the major portion of the 
seedlings, and that this feature is not confined to Centranthus is shown by 
the fact that Hill and de Fraine ( 7 ) record a specimen of Silene Schafta 
which although triarch throughout is secondarily dicotylous, doubtless 
through the complete fusion of two of the cotyledons, the double origin of 
the abnormal ‘ cotyledon 5 being indicated by its much larger size. It will 
be evident therefore that no seedling can be classified accurately solely by 
its external appearance. 
Another feature of interest is found in those hemitricotyls and tricotyls 
in which one of the vascular bundles, on entering the hypocotyl, retains its 
collateral structure. This condition suggests comparison with the class of 
cotyledon styled ‘subsidiary’ by Hill and de Fraine (6), and allowing for 
the much earlier formation of the solid xylem plate in Centranthus the 
structure seems not unlike that described in some of those ‘ subsidiary * 
cotyledons. 
From the description given by Hill and de Fraine it appears that they 
consider this type of cotyledon may be produced by either — 
(i) A lateral splitting off of tissues from a normal cotyledon, a 
behaviour suggested by the structure found in Pinus Montana, var. gallica , 
series B, and in Larix etiropaea , series C ; or (a) a displacement of an epi- 
cotyledonary leaf to the cotyledonary level, as in Cedrus Deodara , series A, 
and Pinus Pinea , series C. 
To these a third alternative may be added, namely, that the member 
is a cotyledon the vascular system of which is behaving anomalously. 
