A natomy of Teratological Seedlings . I. 515 
(a) In the seven seedlings comprising the first group the normal 
cotyledon has a typical double bundle, while the midrib of each half of the 
bifurcated cotyledon consists of a collateral bundle. Towards the base of 
the cotyledon, after fusion of the two halves has occurred, the collateral 
bundles approach one another, while the protoxylems rotate towards the 
middle line, and fuse so that ultimately the two function as a double bundle, 
Fig. i. a, b, c. Hemitricotylous seedlings, showing three stages in the division of the 
abnormal cotyledon. 
Fig. 2 . a-f. Hemitricotyl, Type a. Diagrams a, b , c Show the asymmetrical union of 
two half cotyledons; the normal cotyledon is not shown. Diagrams d, e, f show the 
structure lower down in this seedling. 
producing, together with the double bundle of the normal cotyledon, 
a typical diarch structure (Fig. 3). 
This condition is found in seedlings having the cotyledon split nearly 
to the base, as well as in those which are merely notched, the only variation 
being in the level at which the two collateral bundles unite. This union 
may occur in the lower portion of the cotyledon lamina, in the petiole, or 
even at the apex of the hypocotyl, but the point of fusion bears no close 
