ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 61 



shaped chromosomes lying close on one another. The chromosomes 

 gradually disperse until they are evenly distributed through the nucleus. 

 Many nucleoles are now visible, and cell-division commences. The 

 chromatin elements gradually form a knot ; the nucleoles decrease in 

 number, but increase in size. In the daughter-nuclei the chromosomes 

 again make their appearance in rings or in paired strings ; the nuclear 

 membrane disappears, and the nucleoles lose their staiuability. The 

 division of the daughter-chromosomes appears to take place in the same 

 way as that of the mother-chromosomes. 



Middle Lamella of Cells. * — C. E. Allen differs from both of the 

 current explanations of the differentiation of a central layer in the mem- 

 brane of cellular tissues, differing, in its optical and staining properties, 

 from the layers on each side of it, viz. — that it is an intermediate product, 

 a Zwischensubstanz, distinct from the cell-walls proper, and that it is a 

 cementing substance for keeping them together. The author details the 

 results of observations made on a number of woody plants which show 

 that this layer is, from a chemical point of view, of a pectic nature, and 

 that it is a plastic portion of the cell-wall itself, capable of increase or 

 decrease, and of alterations in chemical composition, adapting the cell- 

 wall to the changes in size and form of the protoplast itself. The staining 

 reactions at various stages of development are given in great detail. 



Researches on Cellulose, f — C. F. Cross and E. J. Bevan publish a 

 supplement to their work issued in 1895, giving an account of all the 

 observations and discoveries of importance that have been made during 

 the five succeeding years. It is divided into the following sections : — 

 Introduction, dealing with the subject in general outline ; General 

 chemistry of the typical cotton cellulose ; Synthetical derivatives : 

 sulphocarbonates and esters ; Decompositions of cellulose such as throw 

 light on the problem of its constitution ; Cellulose group, including 

 Hemi-celluloses and Tissue-constituents of Fungi ; Furfuroids : i.e. 

 Pentosanes and furfural-yielding constituents generally ; the Ligno- 

 celluloses ; Pectic group ; Industrial and Technical : General review. 

 Indices of authors and subjects are appended. 



(2) Other Cell-contents (including Secretions). 



Crystalline and Crystalloid Substances in Plants.^ — Dr. H. Kraemer 

 has studied the structure and mode of formation of these substances. 



Sphere-crystals are spherical aggregates of crystals with sharp 

 angular contours, which are made up of but one substance, the molecule 

 of which is simple, or at least not very complex. It includes carbon 

 compounds as well as inorganic substances. Some of these substances 

 are soluble in water (the glucosides and alkaloidal salts, amygdalin, &c.) ; 

 while others are insoluble (calcium phosphate and oxalate, the alkaloids 

 such as strychnine, berberine, &c). Spherites are distinguished from 

 sphere-crystals in having a more complex constitution, and in the 

 individual crystals having a somewhat rounded outline, or being 



* Bot. Gazette, xxxii. (1901) pp. 1-34. 



t Researches on Cellulose, 1895-1900, London, 1901, vii. and 180 pp. 

 J Proc. Acad. Nat. Sci. Philadelphia, liii. (1901) pp. -150-6. Cf. this Journal, 

 1900, p. 47S. 



