ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 61 



Cystolith-formation in the Cistacese.* — M. Gard has examined 

 the silicified thickenings which occur in the leaves of many CistaceEe. 

 They are found in epidermal cells, stomata, palisade, and spongy 

 parenchyma, and although they have no pedicel, the larger formations 

 greatly resemble true cystoliths. They are not usually confined to a 

 single cell, but extend through several adjacent cells. They often 

 surround a stoma or the base of a hair. They are analogous to similar 

 formations which have been noticed in the Oleacete, Santalacese, 

 Loranthaceae, and Euphorbiacea3. Although they cannot be utilised in 

 the distinction of species, they appear to be constant in individuals 

 of very different origin, e.g. in C. monspeliensis they always abound in 

 the lower epidermis, while the C. populifolius they surround the stomata ; 

 it may thus prove useful to mention them in anatomical descriptions. 



Structure and. Development. 

 Vegetative. 



Centripetal Wood in the Conifer ae.-j-— Ch. Bernard has investigated 

 various members of the Conifers in order to discover how far centripetal 

 wood is developed in the bracts and scale-leaves. The present research 

 is a continuation of that published by the author in 1904, and is 

 especially intended as a reply to the criticisms of Bertrand. The latter 

 w r as of the opinion that the so-called centripetal wood was nothing 

 but a diffused mass of cork, developed for physiological reasons. The 

 author re-affirms his former statements, and contends that centripetal 

 wood still exists, although sometimes in a much modified form, in the 

 leaves of conifers, and more particularly in the leaf -tips ; the exist- 

 ence of such wood in the bracts and scale-leaves is also clearly demon- 

 strated. The plants examined include Agathis borneenxis, Katakidozaniia 

 sp., Aru in- aria imbricata, A. Bidwillii, Thuya occidental is, Larix decidaa, 

 Gedrus Libani, Picea orientalis, P. excelsa, Abies cephalonka, Pin us 

 Montana, P. Oembra ; the author believes that the confirmatory results 

 given by these genera tend to show T that all the Coniferas have preserved, 

 at least in those organs which have retained their ancestral characters, 

 the typical centripetal xylem. 



Stem of Ibervillea Sonorge.J — A. A. Knox has investigated the 

 stem-structure of Ibervillea Sonorce. The author describes the exterior 

 of the stem as having a tendency to the seven-angled type, but later on 

 it is terete. There are five bundles forming an outer ring, while the 

 number in the inner ring varies from five to nine. There are endocyclic 

 and ectocyclic sieve-tubes, as well as commissural sieve-tubes connecting 

 the phloem of adjacent bundles. There is an active inner cambium. 

 The sieve-tubes gradually become obliterated and serve as a secretory 

 system, and their contents provide wound-gum. There is a periderm 

 with phellogen and phellem. There is no true bark nor any deep 

 phellogens. There is a large deposition of calcium carbonate which 

 gives the surface of the stem a greyish appearance. The meristematic 



* Comptes Rendus, cxlv. (1907) pp. 13G-7. 



t Bot. Centralbl., xxii. (1907) pp. 211-44 (50 figs.). 



% Bull. Torrey Bot. Club, xxxiv. (1907) pp. 329-44 (1 pi. and 2 figs.). 



