60 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Nodes and Internodes of the Stem of Dicotyledones.* — M. A. 
Prunet finds, as a general rule, a marked difference between the vessels 
of the nodes and those of the internodes, in the vascular bundles of the 
aerial parts of plants. In the nodes they are generally smaller and more 
numerous. The parenchymatous tissues, aud especially the cortex, are 
greater in volume in the node ; and the medullary rays are larger, or 
even more numerous. In the underground nodes this difference almost 
entirely disappears. The woody parts of plants always contain dormant 
buds connected with the pith by a broad medullary ray which springs 
from a foliar medullary ray. They are formed at all ages of the plant, 
and are met with, not only in the axil of ordinary leaves, but also at the 
base of rudimentary leaves and of bud-scales. 
Course of the Vascular Bundles in the Leaves of the Hippo- 
castaneae.j — According to M. A. Trecul, in AEsculus and Pavia the 
primary bundles increase basifugally in the bud-scales, which are abor- 
tive leaves. In the leaves themselves, the mode is different in the two 
genera. In JEsculus (Hippocastanum and rubicunda), the primary vessels 
belonging to each separate leaflet are formed first of all in the petiole, 
and descend thence into the stem, and it is only later that other vessels 
make their appearance on the sides of the median vein of each leaflet. 
In Pavia on the other hand (macrostachya, lutea, rubra, and californica), 
both the primary and secondary veins have frequently a double mode of 
growth, the upper part appearing first and growing basipetally, and this 
being then met by the lower portion with basifugal growth ; or the 
order of development is the reverse. The first vessels appear in the 
veins of the middle portion of the leaf ; in the other veins the vessels 
appear basifugally in the upper part, basipetally in the lower part of 
the lamina. 
Free Vascular Bundles.^ — Herr K. Muller records the existence of 
free vascular bundles in the leaf-stalk of several species of Umbelliferae 
( Heracleum , Arcliangelica), and Composite ( Cynara ). 
Mucilage-cells of Orchidaceae.§ — Herr C. Hartwich has investigated 
the constitution of the mucilage-cells in the tubers of Orchidaceae 
(Orchis Morio and lati folia). He finds that a drop of mucilage is first 
formed round the bundle of raphides in the middle of the cell, which 
grows, and forces the protoplasm with the nucleus towards the cell-wall, 
inclosing the protoplasm threads which stretch towards the periphery. 
Only in the rare cases where the cell does not contain raphides does the 
formation of mucilage appear not to commence in the middle. The 
protoplasm threads, observed by Meyer in the mature cells, stretching 
towards the interior appear to be the result of the action of alcohol. 
The mucilage takes a yellow colour with iodine and sulphuric acid ; 
with aqueous solution of eosin it is stained yellow-red in young, rose- 
coloured in older cells, thus affording a contrast to the mucilage of the 
Cactaceae. 
* Ann. Sci. Nat. (Bot.1, xiii. (1891) pp. 296-373 (4 pis.). 
j Comptes Rendus, cxii. (1891) pp. 1406-14. 
f Verhandl. Bot. Ver. Prov. Brandenburg, 1S91, pp. viiL-ix. Cf. this Journal, 
1890, p. 198. 
§ Arch. Fharm., xxviii. (1890) pp. 563-72 (1 pi.). See Bot. ContralbL, 1891, 
Beih., p. 349. 
