742 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of an endodermal sheath surrounding each fibrovascular bundle, and 
of a continuous pericycle in the median bundle ; (6) by the lacunae being 
arranged in three rows at the base of the lamina, and in a single row 
towards its apex ; (7) by the presence below the epiderm of bundles of 
fibres which are sometimes lignified ; (8) by the presence of secretory 
cells. Two other species of the same genus are described : — C. rotundata, 
with 10-13 veins, and C. serrulata , from the Red Sea and Indian Ocean, 
with 15-17 veins. 
The genus Posidonia includes two species — one Mediterranean and 
one Australian. The leaf of P. Caulini is characterized (1) by a sheath 
with free edges, (2) by a large lamina, (3) by 13-17 parallel veins, 
(4) by the median vein being prolonged but not quite reaching the apex, 
(5) by a well-developed endodermal sheath round each fibrovascular 
bundle, (6) by numerous lacunae, (7) by the structure and position of 
the fibres of the lamina, (8) by the numerous secretory cells, (9) by the 
absence of transverse perforated diaphragms. P. australis is easily dis- 
tinguished by its leaf from P. Caulini. 
Finally, in his conclusions, the author contrasts the three genera 
described in this paper. The species can be distinguished from each 
other by the arrangement of the parenchyme and the lacunae, by the 
nature of the fibrovascular bundles, by the presence or absence of 
secretory cells, and by the character of the endodermal sheath when 
present. 
Pitchers of Dischidia.* — Prof. F. Delpino discusses the function of 
these organs, and comes to a conclusion different from that of Treub, 
whose observations he conjectures were made on plants growing in 
unnatural conditions, and to a certain extent atrophied. Delpino finds 
in the pitchers a large quantity of detritus consisting of the remains of 
ants, hymenoptera, and other insects, a portion of which he believes to 
have been truly digested, and to have entered into the composition of the 
tissues. The principal object of this supply of nutriment appears to be 
to furnish material for the numerous adventitious roots of this epiphytic 
plant. 
Resinous Leaves, j — Herr G. Volkens has examined the structure of 
a large number of plants with resinous leaves belonging to many 
different natural orders, and classifies them under the four following 
heads : — (1) The secreting organs are internal glands ( Hypericum 
resinosum and possibly Vernonia viscidula') ; (2) a hypodermal tissue 
is filled with resin ( Fabiana squamata, Sarcocaulon rigidulum ); (3) the 
young leaves are covered with resin excreted by the stipules ( Larrea , 
Zygophyllese) ; (4) the leaves themselves are provided with secreting 
glands (all the remaining examples). Hanstein’s “ blastocolla ” consists 
usually of a mixture of mucilage and resin, the former resulting from a 
decomposition of cellulose, the latter already fully formed in the 
“ colleters.” Plants with viscid or resinous leaves are almost invariably 
natives of arid climates, and the secretion is obviously a provision 
against excessive transpiration. 
* Malpighia, iv. (1890) pp. 13-7 (1 pi.). 
t Ber. Deutsch. Bot. Gesell., viii. (1890) pp. 120-40 (1 pi.). 
