Seedling Anatomy of Certain Sympetalae. II. 313 
In one or two cases there were indications near the root-apex of further 
reduction to a diarch arrangement. 
Bidens pitosa , Linn. Seedlings 5-7 cm. long, slender, and each 
possessing two equal, linear seed-leaves which unite at the base to form 
a cotyledonary tube. 
Near the apex of the seed-leaf there are three vascular bundles — the 
usual median strand and two smaller laterals— formed by division of 
a single large strand. At a lower level, small median bundles occur which 
subsequently unite with the median strand. In the upper part of the hypo- 
cotyl the median bundle divides, and the branches pass to the corners of the 
almost square stele, leaving behind a small strand of protoxylem in the 
cotyledonary plane (Diagram 7, I, II). The metaxylem branches thus 
formed consist in each case of 1-3 lignified elements, the protoxylem of 
only a single vessel. The lateral strands from the two seed-leaves fuse in 
pairs in the cotyledonary tube. At a lower level, the metaxylem in each 
case disappears, leaving behind a single, more or less lignihed, protoxylem 
