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SUMMARY OF CURRENT RESEARCHES RELATING TO 
do not form a complete system of tubes through the whole plaut, but 
are interrupted here and there by septa which have not been completely 
absorbed. The greatest length of vessels measured was in Aristolocliia 
Sipho 2* * * § 26 m., and in Bobinia jpseudacacia 0*69 m. ; the shortest in the 
leaf-stalk of Areca lutescens 3 • 2 cm. The maximum length was attained 
in branches four years old. 
Assimilating Tissue of Mediterranean Plants.* — M. W. Russell 
finds that in the littoral plants of the Mediterranean region the presence 
of an assimilating tissue containing chlorophyll in the stem is more 
common than in plants of temperate climates, thus presenting an 
approach towards the special characteristic of desert plants. Several 
types of this structure are described. 
Formation of Secondary Vascular Bundles in Dicotyledons.! — 
Herr K. Schilberszky finds, from experiments on herbaceous dicotyle- 
donous plants (chiefly Phaseolus vulgaris and multijlorus ), that, if the 
vascular cylinder of the epicotyl or hypocotyl is cut through, a definite 
portion of the permanent tissue — viz. the groups of cells which lie 
nearest to the innermost layers of the parenchymatous primary cortex 
close to the phloem-bundles — may be incited to divide, and may hence 
become a secondary meristem. This secondary meristem behaves in the 
same manner as the cambium, its elements becoming transformed more 
or less rapidly into xylem and phloem. The initial layer of these extra- 
fascicular vascular bundles is the starch-sheath, which is specially 
adapted, by its store of reserve-materials, for the development of their 
procambial tissue. 
Sieve-like Pores in Tracheal Xylem-elements4 — In a large number 
of woody leguminous plants, and a few belonging to other natural orders, 
Herr B. Jonnson finds, within the tracheal system, a structure of the 
membrane resembling to a great extent the perforation of sieve-tubes. 
These elements he proposes to term sieve-pore vessels and sieve-pore 
tracheids. The purpose of these pores appears to be to facilitate the 
processes of transport and metastasis, and the passage of air. It is 
probable that, as long as cells are in a living condition, all those which 
form a uniform tissue are in communication with one another by proto- 
plasmic connections. 
(4) Structure of Organs. 
Principles of Teratology.§ — M. D. Clos proposes a classification of 
teratological phenomena on a natural system, which he bases on a collo- 
cation of all the changes which can take place in any one individual 
organ. In many cases certain anomalies are characteristic of entire 
families, as* well as of genera and species; and the affinity of families 
and genera is often indicated by the similarity of their anomalies. On 
the other hand, some nearly related families are distinguished by the 
differences in their characteristic anomalies. Varieties and species, and 
even genera, have been constructed out of teratological phenomena. The 
* Comptes Rendus, cxv. (1892) pp. 524-5. 
t Ber. Deutsch. Bot. Gesell., x. (1892) pp. 424-32 (1 pi. and 1 fig.). 
X Tom. cit., pp. 494-513 (1 pi.). 
§ Mem. Acad. Sci. Toulouse, iii. (1891) pp. 163-208. 
