14 BOTANICAL GAZETTE [MARCH 
leaf, but none accompanies the smaller veins. No stereome is 
present in the leaf. The chlorenchyma is quite compact throughout 
and is differentiated into a typical palisade tissue of two strata on 
the upper face of the blade and around the nerves. Between the 
nerves on the lower face of the blade the chlorenchyma consists of . 
a pneumatic tissue of more or less oblong cells, with the intercellular 
spaces quite distinct but not so wide as in the other genera examined; 
raphides were observed in the pneumatic tissue, but not many among 
the palisades. 
The mestome strands are collateral and surrounded by a very 
large celled and thin-walled parenchyma sheath, some of whose cells 
contain tannin; the midrib is the largest and its outline in cross- 
section is oval, while the others are much thinner and orbicular. 
The venation of the leaf is difficult to observe without sepa- 
rating the chlorenchyma from the veins, since the cross veins 
(secondaries) are so exceedingly thin and completely surrounded 
by chlorenchyma. The cross-veins are so numerous, indeed, that a 
transverse section of the blade shows their parenchyma sheaths so 
distinct “longitudinally” that the leaf is almost divided by them into 
two zones. 
The stipules are divided into several bristles, which are termi- 
nated by a pointed hair, and a few (mostly three) glandular hairs 
occur at the base between the bristles; the structure of these glandu- 
lar hairs is like those of Houstonia (fig. 6), but the stalk is much 
longer in Diodia. According to WarMING,'? D. radicans Cham. et 
Schl. possesses dorsiventral leaves with the pneumatic tissue con- 
sisting of stellate cells with very wide intercellular spaces; moreover, 
the stomata, which are said to have no subsidiary cells, are confined 
to the dorsal face; hence the leaf is strictly dorsiventral. 
Diodia teres, therefore, shows the following points of interest: the 
structure of the epidermis of the leaves; the approximately isolateral 
blade with stomata on both faces and with the palisade tissue partly 
extending to the dorsal epidermis; and the scant development of col- 
lenchyma and total absence of stereome in the leaves as well as in 
the internodes. 
2 Halofyt-Studier. Kgl. Danske Vid. Selsk. Skr. VI. 8:187. 1897. 
