484 RECORD OF CURRENT RESEARCHES RELATING TO 



as, for instance, in the guard-cells of the stomata, where it has erro- 

 neously been stated that the nucleus may disappear while the cell is 

 still in a living state. 



The reagent chiefly employed by Dr. Schmitz for the detection of 

 the cell-nucleus is an aqueous solution of hfematoxylin, to which in 

 some cases a small quantity of alum was added, and a few drops of 

 the mixture then mixed with the glycerine. This mixture was applied 

 directly to the cell after killing it with alcohol or osmic acid. 

 When properly applied, the interior of the cell-nucleus then assumes 

 an intense blue colour, the mass of the nucleus is more feebly coloured 

 blue, while the rest of the protoplasm remains uncoloured. This 

 preparation is especially useful for detecting the division of the 

 nuclei. 



Embryology of the Archegoniatae.* — K. Goebel gives a brief 

 resume of the present state of our knowledge of the Archegoniatfe, 

 including in this term the Vascular Cryptogams and Muscinete (Cor- 

 mophytes). It is based mainly on the published observations of 

 Kienitz-Gerloff, Sadebeck, Leitgeb, Hegelmaier, Pfeffer, of the author 

 himself, and others, 



Cryptogamia Vascular ia. 



Bundle-sheath in Polypodiaceae.t — In all the Polypodiacete the 

 fibrovascular bundles, both of the frond and of the rhizome and roots, 

 are surrounded by a bundle-sheath which differs essentially from that 

 of monocotyledons and dicotyledons. Prantl considers the bundle- 

 sheath of ferns to have its origin in the jH-ocambium, while Russow 

 refers it to the fundamental tissue. An examination of a number of 

 species has led Dr. J. E. Weiss to agree rather with the former view, 

 and to regard it as either a product of the procambium or as an inde- 

 pendent layer of tissue. The following are his reasons : — 



The arrangement and size, as well as the peculiar behaviour of 

 the innermost cells of the fundamental tissue, in contrast to the small 

 size of those of the bundle-sheath, and the position of the radial walls 

 of the latter, do not favour the idea that the two tissues have a 

 common origin ; while in the case of monocotyledons and dicotyledons 

 it is easily proved that the bundle-sheath originates from the funda- 

 mental tissue. 



The bundle-sheath, with the cells which mostly stand in perfectly 

 radial rows, originates from a single cell ; but these cells are larger 

 than the phloem-cells which are irregularly arranged adjacent to them 

 within, but otherwise behave in the same manner. 



The bundle-sheath originates at the same time as the procam- 

 bial fibrovascular bundle, when the cells of the fundamental tissue 

 have already attained a certain size and development. 



If the bundle-sheath and its sister cells belonged to the funda- 

 mental tissue, they would be formed in centripetal order ; but this is 

 not the case, at least in Pteris aquilina. 



* ' Arbeit. Bot. Inst. Wiirzbuig,' ii. (1880) p. 437. 

 t 'Flora,' Ixiii. (1880) p. 119. 



