ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 215 



cells. The crystals have the form of more or less elongated four-angled 

 prisms ; the cell-wall is suberised ; the cells are entirely or largely filled 

 by the crystals ; they are dead, and usually contain, in addition to the 

 crystals, nothing but air ; each crystal is surrounded by a membrane-less 

 envelope, which is often also suberised. The crystals are composed of 

 calcium oxalate, and are probably an excretion product. The membrane 

 usually consists of two lamellaa, the inner one of which is suberised, but 

 not the outer one. It is probably formed by modification from the cell- 

 wall. This membrane is not always present ; when there is one it can 

 be detected by dissolving out the crystal by hydrochloric acid. The 

 distribution of the crystal-cells in the tissues varies in different species. 

 A number of special cases of their occurrence are described in detail. 



Interxylary Leptome of Dicotyledons. * — Herr B. Leisering has 

 made an exhaustive examination of those exceptional cases where, in the 

 vascular bundles of Dicotyledons, a portion of the phloem elements 

 occur, as larger or smaller islands, enclosed in the xylem, and therefore 

 within the cambium, with a view to determine the mode in which this 

 has been effected. The phenomenon occurs in a very large number of 

 genera scattered through many natural orders, the specialities of which 

 are described in detail. 



Of the three modes in which it has been suggested that these islands 

 may have been formed, the author finds evidence, in his investigations, 

 of two only, viz. : — (1) The pbloem is formed, in the typical manner, 

 on the outside of the bundle, but has been bridged over by an outer layer 

 of cambium ; (2) Subsequent differentiation of tissue formed endo- 

 genously, which at first partakes of the character of xylem-parenchvme. 

 The first type occurs in the Chenopodiaceae, Amaranthaceae, Phytolac- 

 caceae, Nyctagineae, Melastomaceae, Loranthacese, Combretaceae, Logani- 

 aceae, &c. ; the second in the Cruciferas, Cucurbitaceae, Campanulaceae, 

 Solanaceae, Gentianaceae, Le'guminosae, Malpighiaceae, Apocynaceae, As- 

 clepiadeae, Acanthaceae, ifec. As a rule the " island " consists only of 

 sieve-tubes with the accompanying thin-walled cells. Those of the first 

 type are usually nearly circular in transverse section ; while those 

 belonging to the second type have a much more irregular form. 



. Fibrovascular System of the Female "Flowers" of Conifers.f — 

 Mr. W. C. Worsdell has made a careful study of this subject in a 

 number of species belonging to the Araucarieae, Abietineae, Podocarpeae, 

 Taxeae, Taxodineae, and Oupressineae, but is not able to come to a con- 

 clusion from it of the true nature of the so-called female " flower." The 

 Araucarieaa, Podocarpeae, Taxodineae, and still more the Abietineae, 

 afford illustration, in the structure of their vascular bundles, of the com- 

 pound nature of the axial appendage of the female cone, the two foliar 

 organs comprising it being, in the last order, distinct and separable 

 except at the very base, where they are adnate to one another. The 

 Taxeae differ from the other groups in the fact that the sporanges occur 

 in a terminal instead of lateral position with respect to the axis on which 

 they are borne. 



* Bot. Centralbl., Ixxx. (1899) pp. 289-9S, 321-331, 369-7U, 414-22, 405-70, 

 497-503 (3 pis.). 



t Ami. of Lot., xiii. (1899) pp. 527-48 (1 pi.). 



