Sections of the hypocotyl of Ricinus communis are frequently examined as typical of the young stem, in which widely separated vascular bundles are ultimately united by a band of interfascicular cambium, and this by giving rise to secondary tissues connects the xylems and phloems of the primary bundles to form concentric continuous rings.

In the young unthickened hypocotyl of Ricinus there are eight such bundles connected by a continuous starch sheath and one layer of smaller cells immediately inside it. In some sections, however, confusion arises owing to the increase of the number of vascular bundles, and in the case of older hypocotyls these extra bundles are embedded in the cambium ring and have rather the appearance of secondarily formed tissues.

It was in the first instance to clear up the origin of these bundles that, at the suggestion of Professor F. W. Oliver, the following work was begun. Afterwards, as there seemed some advantage in working out in full the arrangement of the vascular system in this plant, which is so frequently used as a dicotyledonous type, it has been followed from the root, through the hypocotyl, to the 1st and 2nd internodes of the epicotyl.

The well-developed primary root of the seedling of Ricinis communis averages about 2 mm. in diameter. About 5 mm. below the junction with the stem it enlarges rapidly to attain the diameter of the hypocotyl, which varies between 4 and 5 mm. It is from this swollen portion of the root that most of the first developed lateral rootlets take their origin.