ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
619 
Vessels may also be found in the rays which separate the xylem-bundlcs 
and in the pericycle of the roots, as in Taxus and Torreya. The stem 
can produce primary extra-xylem vessels in the cortex, in the pericycle, 
and in the pith. 
Extra-phloem Sieve-tubes in the Root of the (Enothereae.* — 
Mdlle. A. Fremont finds that sieve- tubes may occur in the (Enotlierese 
either in the pith of the root, in the secondary xylem, or in the “ ulterior 
pith,” by which term the authoress designates a cellular structure 
sometimes formed in the axis of a root after the separation of the 
vascular bundles which at first formed a closed central cylinder. 
Medullary sieve-tubes in the root have hitherto been only known in 
three families of Dicotyledons, viz. Cucurbitaceac, Loganiacese, and 
Apocynacese. Mdlle. Fremont points out, however, that circummedullary 
sieve-tubes, situated at the internal edge of the primary xylem-bundles, 
exist in (Enothera Fraseri and (E. riparia. Good examples of sieve- 
tubes produced by local differentiation of the secondary woody paren- 
chyme are to be found in (E . parvijiora , cruciata, macrocarpa , Sellowii , 
and Fraseri ; and finally it is pointed out that sieve-tubes exist in a 
region where they have not before been observed, viz. in the ulterior 
pith of the root. A good example of this occurs in Epilobium parvi- 
florum. 
Cystoliths of Ficus, f — Herr A. Zimmermann has examined the 
cystoliths in the leaves of Ficus elastica, and supports Kny’s view that 
the strings which penetrate them in a radial direction at right angles to 
the stratification, are solid, and consist essentially of cellulose, rather 
than Giesenhagen’s, that they are hollow cylinders filled with lime. In 
the Acanthaceas, on the other hand, the radial strings are the part of the 
cystolith which contain the smallest amount of cellulose. 
Commenting on this communication, Herr C. GiesenhagenJ says that 
he thinks that Zimmermann has been led into error by examining only 
cystoliths from which the lime has been removed. 
Herr Zimmermann, in reply, § states that a fresh series of observations 
has confirmed his previous conclusions. 
Supporting-elements in the Leaf. || — M. E. Pee-Laby describes 
special organs of support which he finds in the leaves of Dicotyledons. 
These may either have the form of fibres in the woody pericycle ( Hakea , 
Burcftellia), or may consist of isolated cells. These, again, are either 
simple cells, as in Osmanihus aquifolius, Olea europea , and Phillyrsea , or 
they are branched (spicular cells), as in Limnanthemum nympltseoides , 
Begonia sanguinea , Ternstrcemia japonica, &c. In all cases these organs 
make their appearance only when the leaf is assuming its final form. 
Anatomy of Conifers.^ — Herr F. Berger argues against the correct- 
ness of the distinction drawn by Caspary between two different kinds of 
tracheid in Coniferse, viz. the conducting cells in the medullary sheath 
* Journ. de Bot. (Morot), v. (1891) pp. 194-6. 
f Ber. Deutsch. Bot. Gesell., ix. (1891) pp. 17-22 (1 fig.). 
t Tom. cit., pp. 74-7. § Tom. cit., pp. 126-8. 
|| Comptes Rendus, cxii. (1891) pp. 1276-9. 
% ‘ Beitr. z. Anat.d. Coniferen,’ Halle, 1889, 8vo, 33 pp. See Bot. Centralbl.,xlvi. 
(1891) p. 363. 
