132 Taylor — A Morphological and Cytological 



shows only one strand in each leaf, but as they grow three be- 

 come evident which fuse in the petioles or, lower, in the hypo- 

 cotyl (Figs. 94, 95). The bundles which supply the plumule 

 become less and less prominent as one descends the axis, the 

 xylem disappearing and the phloem fusing laterally with the 

 adjacent bundles supplying the cotyledons (Figs. 96, 97), till 

 at last there is a simple axis with four collateral bundles (Fig. 

 98). These form the four poles of the tetrarch root by simple 

 rotation of the elements (Figs. 99, 100, 101). 



In the same species the tricotyledonous specimen was pre- 

 pared in serial sections, and the vascular strands traced in the 

 same way. In the upper part of the cotyledons there were about 

 the same number of vascular strands as in the cotyledons of the 

 normal form. Toward the petiolar base in two of them the 

 strands partially united (Figs. 102, 103), to reappear again in 

 the hypocotyl as two distinct but closely placed bundles (Fig. 

 104). The third cotyledon possessed a small lobe near the 

 base (Fig. 102) which united with it before union with the axis 

 occurred. In this case the two bundles at the base remained 

 widely separated, a small patch of phloem tissue remaining 

 between them (Figs. 103, 104). There were three plumular 

 leaves, all prominently three-lobed. These had each three vas- 

 cular strands, which remained distinct into the hypocotyl, where 

 the xylem of the lateral members of each group disappeared, 

 and the phloem of these fused with the central member (Figs. 

 102, 103, 104). Instead of becoming united into four bundles 

 in the upper hypocotyl as in the normal specimens, the bundles 

 from cotyledons and plumule formed an irregular ring (Fig. 105). 

 A bend above the base of the hypocotyl made it impossible to 

 determine whether these fused to a regular number in the lower 

 hypocotyl, or, as seems likely from the irregular distribution of 

 the xylem (Fig. 106), merged in the transition zone at the base 

 of the hypocotyl. There the vascular system appeared as an 

 irregular ring, the xylem elements on the inner margin. In the 

 top of the root these passed out toward the periphery at four 

 points (Fig. 107) forming a tetrarch root that was somewhat 

 more irregular in form than the normal (Fig. 108). 



The condition indicated seems to be that of a simple fission 

 of one of the two typical cotyledons carried to its greatest extent, 

 the bundles supplying each part being distinct far down the 



