Phloem: in the Stems of Dicotyledons. II. 423 
medullary strands enter the pith from the vascular ring ; and this latter is 
the case with the bundles of the peduncle. 
Peter made an investigation of the genus Scorzoiiera and concluded 
that the grouping of the species according to the systematists does not agree: 
with that according to anatomical data. He classifies the species into four 
groups according to the arrangement and structure of the bundles of the 
stem : (1) Bundles arranged irregularly in several indistinct series or rings, 
all collateral (2) Bundles in two indistinct series of unequal-sized bundles, 
within or without which lie smaller ones ; (3) One regular series of bundles ; 
phloem-strands scattered in the pith, with or without xylem ; (4) One series 
of bundles only ; no medullary strands ; bundles either collateral or 
bicollateral. 
Col, in an important account of the arrangement of the bundles in the 
stem and le&ves of certain Dicotyledons, cited some interesting facts 
regarding the presence of internal phloem in the leaves and axial organs of 
some Compositae. 
Miss K. Barratt observed in a fragment of an internode of the stem of 
Helianthus annnus the passage of a bundle of the vascular ring into the 
pith, becoming there an amphivasal bundle. She draws no inferences from 
this fact. But the present writer has observed many such cases in other 
plants (cf. Tolpis ), and regards them all as instances of partial reversion to 
the primitive scattered disposition of the bundles composing the main 
vascular system of the stem. It is, perhaps, a more widely-spread pheno- 
menon in the Compositae than is generally' known. 
Miss E. Whitaker studied the structure of the vascular cylinder of the 
stem of species of Solid ago, with special reference to the mode in which the 
leaf-trace bundles leave the vascular ring. She starts out from the a priori 
standpoint that the woody type of stem is the more primitive in the Com- 
positae. There is a single reference to the subject of the present paper, as 
follows : ‘ internal phloem in the leaf-bundles of the cortex is a general 
feature of the genus and probably of the family. It seemingly perpetuates 
a condition which was once characteristic of the bundles of the axis.’ 
Original Observations. 
ClCHORIACEAE. 
Tragopogon pratensis, L. 
The stem of this plant has frequently been selected to serve as an 
example of the occurrence of ‘internal phloem’ immediately within the 
xylem of many of the bundles of the main vascular system, such bundles 
being, therefore, as in Cucurbitaceae, of the ‘ bicollateral * type. As a matter 
of fact, this particular structure is characteristic of only a certain region, viz. 
the higher portion of the aerial stem. The object of the present investiga- 
