732 
Lee. — Observations on the 
pp. 174, 175) the transition phenomena appear to be almost exactly as 
described above for Convolvulus tricolor. In this case also internal phloem 
is present both in cotyledons and in hypocotyl. As the xylem groups of 
each bundle come together at the base of the hypocotyl, the corresponding 
phloem mass passes out between them and joins the external phloem. 
Ipomoea leucantha was described by Lamounette (12, p. 220), and 
appears to differ from I. versicolor only in that ‘ internal ’ phloem is absent 
from the vascular bundles in the cotyledons. 
Ipomoea purpurea , investigated by Gerard ( 7 , p. 369), is not essentially 
different from I. versicolor . 
Cuscuta Epilinum , Weihe. Much is generally known concerning the 
anatomy of Cuscuta . Seedlings of various species were re- 
examined, however, in the hope that a knowledge of the 
seedling structure of other genera might throw some light 
on that of Cuscuta. Unfortunately, no new observations can 
be recorded. Special attention was devoted to C. Epilinum . 
The seedlings investigated were 2-5 cm. in length, were 
quite undifferentiated, and had the appearance of a piece of 
fine string. In one case (Text-fig. 1) the upper part twice 
encircled the stem of the host, and haustoria were beginning 
to form. Internally, most of the tissue was cortical, the 
vascular elements being aggregated into an insignificant axile 
strand. The tissue composing the latter was much reduced, 
and in some cases (lignification being at a minimum) it was 
impossible, in transverse sections, to distinguish between 
wood and phloem. The sieve-tube tissue occupied the peri- 
phery of the stele, and enclosed the undifferentiated vessels, 
in which, however, no order of development could be recog- 
nized. In the upper portion of the larger seedlings the 
vessels became arranged into more or less definite groups, 
each with a little phloem. Up to the present it has been 
impossible to find anything even remotely resembling transi- 
tion phenomena. 
Text-fig. i. 
Cuscuta Epi- 
linum on 
Liman usita- 
tissimum (nat 
size). 
Polemoniaceae. 
No examples from this order were examined during the present research, 
but in Polemonium caeruleum , described by Gerard ( 7 , p. 373), the transition 
follows Type 3. The same remark applies to 
Hydrophyllaceae, 
of which Gerard investigated Hydrophyllum canadense ( 7 , p. 373) ; 
Boraginaceae, 
the same worker taking Lithospermum gremil as his example ( 7 , p. 374) ; 
