43 ° Arber. — On the Roots of Medullosa cinglica. 
plate, and separated by dilated parenchymatous rays, are 
characters common to these two plants. The sieve-tubes are 
also accompanied by a good deal of conjunctive parenchyma, 
as in Heterangium. In Medullosa , however, numerous ‘ secre- 
tory sacs ’ occur between the elements of the bast, and also 
among the cells of the parenchymatous rays, as is clearly seen 
in the photograph. 
The sieve-tubes in the root of Medullosa anglica are, as far 
as I can ascertain, without the apparently thickened walls 
and narrow lumen, which are so characteristic of those of the 
stem 1 . But, like the sieve-tubes of the stem, they have lateral 
sieve-plates, similar to those of the phloem of most recent 
Ferns and Gymnosperms. 
On PI. XX, Fig. 4, a photograph of a drawing of highly 
magnified sieve-tubes from the stem of the Binney specimen 
is shown. The sieve-plates (. sp .) are clearly seen as little 
patches on the lateral walls. 
In the roots, lateral sieve-plates also occur, as is shown in 
the drawing figured on PI. XX, Fig. 5. It is only fair to add 
that Dr. Scott, who has examined the Binney sections, and 
most kindly given me the benefit of his opinion on several 
points in the anatomy of these roots, first recognized and 
pointed out to me the occurrence of lateral sieve-plates in the 
phloem of both stem and roots. I may therefore take this 
opportunity of expressing my thanks to Dr. Scott for much 
help in the examination of this material. 
Lateral sieve-plates have been previously recognized in the 
phloem-elements of the stem of Heterangium tiliaeoides 2 , and 
by Professor Renault 3 in the stem of Poroxylon Edwardsi, 
Ren. As far as I am aware, this is the first occasion in which 
they have been distinguished in the root of a fossil plant. 
The external margin of the phloem-zone is composed of very 
tangentially elongated cells without any radial arrangement. 
1 Scott, loc. cit., p. 90, PI. X, Fig. 3. 
2 Williamson and Scott, loc. cit., p. 762, PI. XXIX, Figs. 37 and 38 a. 
3 Renault, Etud. Gites Min^r. Bass. Houill. et Perm. d’Autun, 1896, p. 282, 
PI. LXXIV, Fig. 1 1. Also Bertrand and Renault, Recherches sur les Poroxylons, 
Arch. Bot. N. France, 1886, Figs. 192-3. 
