ZOOLOGY AND BOTANY, MICROSCOPY, ETC. .. $81 



composing the oxygenated water, and thus indirectly producing oxidation. 

 This substance, which the author calls lejrfomin, can he isolated in the 

 form of a white amorphous powder. 



The function of sieve-tubes as conductors of food-material is dis- 

 cussed at length, and special attention is paid to the medullary and 

 intraxylary sieve-bundles. 



Contrary to the statement of some observers, the author never finds 

 the phloem-bundles entirety wanting in aquatic Phanerogams, though 

 they are greatly simplified in structure, and may often bo reduced to a 

 single sieve-tube. 



Pericycle* — An account by Herr H. Fischer of the structure of the 

 pericycle in the free axial organs closes with the following general 

 remarks. In about 32 p. c. of the Dicotylcdous examined, ;tn endo- 

 denn was more or less distinctly detected, indicating the distinction 

 between the cortex and the central cylinder. The so-called pericycle, 

 by its position between the limit of the cortex and the ring of vascular 

 bundles, is allied with the pericambium of the root. Considered histo- 

 logically, genetically, and as a formative region, there arc no common 

 characteristics of pericycle and pericambium. In Monocotyledons, 

 Conifers, and about G8 per cent, of the Dicotyledons examined, there 

 is no characteristic limit to the cortex. The mechanical ring of Mono- 

 cotyledons is from no point of view allied to the pericambium. 



Increase of Tissues outside the Cambium-layer, f — According to 

 M. H. Devaux, the increase in diameter of the tissues situated outside 

 the cambium-layer [in a Dicotyledonous stem] is not effected mainly 

 by any rupture of the tissues, nor by the formation of lacunae, though 

 these are not infrequent, but by a tangential growth, accompanied by 

 the more or less frequent production of radial septa. This increase 

 takes place in general only in the outermost layers in contact with the 

 periderm (bark, pericvele, or liber). In the more interior parts it is 

 always localised, chiefly between the pericyclie or liber-bundles ; these 

 regions of increase, prolongations of the medullary rays, being often 

 readily visible. When sclerotised sheaths occur in the pericycle or liber, 

 these are burst through by the tangential growth. 



Crystal-cells of the Pontederiacese.ij: — Herr \V. Eotkert has investi- 

 gated these structures, chiefly in the case of Eirlthornia speciosa. They 

 are peculiar to the order, but do not occur in all the genera. They are 

 found chiefly in the lamellar parenchyme of the petiole and lamina of 

 the leaf, and in the transverse septa and lateral walls of the air- 

 chambers ; their axis being usually at right angles to the wall. Each 

 crystal is envekmed in a closely fitting homogeneous envelope, formed 

 out of the protoplasmic layer nearest to the crystal after its formation. 

 The crystals consist of calcium oxalate, but are quite distinct from 

 raphids ; they are very much larger and are usually solitary in each 

 cell, very rarely more than two. 



Injuries produced by Heterodera radicicola.§ — M. M. Molliard 

 calls attention to the pathological structures induced by the attacks of 





* Piingsheim's Jalirb. f. wiss. Bot., xxxv. (1900) pp. 1-17 (1 pi.). 

 t Mem Sci. Phvs. et Nat. Bordeaux, v. (1899) pp. 47-58. 

 t B"t. Ztg., lviii. (1900) 1" Abt., pp. 75-lOb 1 (1 pi. and 2 figs.). 

 § Rev. Gen. de Bot. (Bonnier), xii. (1900) pp. 1:37-115 (1 pi.). 



A 2 



