339 
Anatomy of Teratological Seedlings. III. 
a cotylar anatomy which is indistinguishable in essentials from that of 
a single cotyledon of a normal dicotyl, and possesses, in common with the 
remaining members of the group, a single median axillary bud. Moreover, 
the group as a whole exhibits an admirably graded series of forms of 
progressively greater complexity, the final member of which is tetrarch 
owing to the increase in importance of the lateral and marginal strands 
respectively. If these seedlings were the ultimate products of a reduction 
series it would be reasonable to anticipate the development of a relatively 
stable type, whereas the reverse, as we have seen, is the case. A further 
point is that between the most extreme member of the undoubted syncotyls 
and the group under consideration there is a wide gap unbridged by any 
transitional forms whatever. It is recognized that negative evidence of this 
type is always liable to be shaken by subsequent discoveries, but it is fair to 
expect that some at least of the specimens studied would have furnished 
evidence of a double origin, since it is difficult to conceive of a cotyledonary 
union so intimate that no part of the seedling anatomy would reveal it, 
especially in view of the fact that syncotyly is not normal for the species. 
The facts which tell against the above interpretation are three in 
number, namely : 
(i) The absence of material showing any trace of suppression of one of 
the cotyledons. (This, as negative evidence, is of course open to similar 
objections to those indicated in the previous paragraph.) 
(ii) The position of the first epicotyledonary leaf. 
(iii) The character of the modifications of the epicotyl. 
The second and third of these points will be dealt with subsequently. 
With regard to the first, although a careful search was made and a number 
of seedlings exhibiting a difference in the size of the cotyledons were 
examined, no evidence of a convincing character was obtained. Where the 
discrepancy in the size of the cotyledons was not very pronounced the 
vascular structure was not affected, and where the cotyledon had remained 
very small this was due, with one exception, to traumatic causes. The 
injury responsible for the arrested growth as a rule involved a more or less 
complete severance of the median petiolar bundle, and often of one of the 
lateral bundles as well. The result was that, though the cotyledon became 
green, it retained its intraseminal form and size and was packed with starch 
grains owing to the interference with the channels of translocation. The 
one exceptional case, although not bearing directly on the origin of the 
group under discussion, is of sufficient interest to merit description. Of the 
two cotyledons, one was normal in size, whilst the other was small and was 
flexed downwards by the petiole (Figs. 8 a, b , c ). Serial sections revealed 
a curious anomaly in the vascular supply of the reduced cotyledon, the 
midrib consisting of a collateral bundle flanked, in the petiole, by three 
smaller bundles on either side (Fig. 107). At the apex of the hypocotyl 
