608 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(4) Structure of Tissues. 



Concentric Vascular Bundles.* — Herr M. Moebius classifies the cases 

 where the fibrovascular bundles have a central phloem and a peripheral 

 xylem under five groups, viz. : — (1) The rhizome of Monocotyledons ; (2) 

 Monocotyledons with secondary growth in thickness ; (3) Dicotyledons in 

 which vascular bundles are formed — usually only at a later period — in the 

 interior of fleshy stems and roots ; (4) Bundles in the pith of dicotyledonous 

 stems (this is by far the most numerous group) ; and (5) Cases difficult to 

 group elsewhere ; such as the bundles in the pith of the axis of the 

 inflorescence of Bicinus (in these the concentric arrangement is often most 

 strongly displayed). A systematic review follows of the families in which 

 bundles of this kind occur. 



Structure of Stomata.f — Dr. G. Haberlandt, referring to Schwendener's 

 description of the structure of stomata,J points out that in addition to the 

 outer " hinge," there is often, in addition, an " inner hinge," which may be 

 simply a narrow strip of cell-wall, or may consist of the whole inner wall 

 of the adjacent cells which has remained thin ; a very good example of 

 this structure is furnished by the stomata in the stem of the flax-plant. 



The structure is described in detail of the stomata in the leaves of a 

 large number of floating plants. The author asserts that the usual state- 

 ment that these stomata have no power of opening or closing is not correct ; 

 the power is, however, much more feeble, and is lost at an earlier period, 

 than is the case with land-plants. It is not dependent also, as in most 

 stomata, on the contact of the bulging ventral walls of the guard-cells, but 

 entirely on the more or less complete approximation of the greatly widened 

 outer cuticular bands. The differentiation of the entire stoma into anterior 

 chamber, central fissure, and posterior chamber, is nearly or entirely lost. 

 The purpose of this structure appears to be to prevent the capillary stoppage 

 of the fissure with water. 



Clothing of Intercellular Spaces.§ — M. C, van Wisselingh has ex- 

 amined, by the use of staining reagents, the nature of the layer 

 which so often clothes the wall of intercellular spaces. In most cases he 

 finds it to consist of the lignified outermost layer of the cell-wall, often 

 easily separable and sometimes puckered into folds by the unequal growth 

 of the subjacent layer. In the angle where two cells meet it is often raised 

 up so as to form secondary intercellular spaces. A lignified outer layer of 

 the wall adjoining intercellular spaces was determined by the use of 

 reagents in the bark of Samhucus nigra, Ligustrum vulgare, and Aucuha 

 japonica, in the cortex of the rhizome of Convallaria majalis, and of the root 

 of Menyanthes trifoliata, and in the parenchymatous cells of the mid-rib of 

 the leaf of Aucuha. 



In other cases, especially in the neighbourhood of the stomata, this 

 layer consists of a suberized or cuticularized substance, as in the large 

 intercellular spaces in the leaf-stalks of NymjyJisea odorata, and in many 

 leaves. An apparently protoplasmic layer in the intercellular spaces was 

 seen only in the root of Lycopus europseus. 



Van Wisselingh's observations agree, therefore, rather with those of 

 Schenk than of Eussow. He confirms Gardiner's observation that in 

 Ligustrum vulgare the clothing of the intercellular spaces consists of a 

 lignified lamella of the cell- wall. 



* Uer. Deutsch. Bot. Gesell., v. (1887) pp. 2-24 (2 pis.). 



t Flora, Ixx. (1887) pp. 97-110 (1 pi.). | See this Jouiual, 1882, p. 216. 



§ Arch. Neerlaud., xxi. (1887) 15 pp. and 1 pi. Cf. this Journal, 1886, p. 471. 



