ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 661 



peculiarities of structure in the following points : — General cliiferentiation 

 of tlie tissues ; epidermal tissues ; fundamental tissue ; vascular bundles, 

 with respect to their course, the various tissues of which they are com- 

 posed, and the structure of their elements. He considers that the most 

 important characters in the differentiation are to be derived from the 

 epidermal tissue. The various points of structure are described in great 

 detail. 



Fibres and Raphides in Monstera.*— Mr. W. S. \Y indie describes 

 the presence in the exocarp or inedible portion of the fruit of 3Ionstera 

 deliciosa not only of raphides, but also of slender, sharp-pointed, needle- 

 like cells or fibres, apparently half-imbedded in the large-celled paren- 

 chymatous tissue. It is these chiefly which cause the sharp stinging 

 sensation in the tongue and palate when this outer coating of the fruit 

 is taken into the mouth. 



(4) Structure of Org-ans. 



Obdiplostemonous Flowers.f — By this term Herr E. Schumann 

 understands those flowers in which there are two whorls of stamens, and 

 the carpids are opposite the members of the outer whorl. This structure 

 occurs in many orders of Apopetal* ; among Gamopetalte only in the 

 Bicornes (Eubiaceae, &c.) ; in Monocotyledones it is unknown. From 

 the numerous cases observed by the author he holds that the law of 

 alternation of members of adjacent whorls has been too absolutely laid 

 down by morphologists ; it is broken through where the members of the 

 preceding whorl are very small, or when they are of cap-like form. 

 This is also the case with regard to the law of acropetal succession in 

 the development of the different organs of the flower, which may be 

 interrupted by the interposition of members of additional whorls. He 

 regards contact alone as sufficient to determine the position of the 

 carpids in isomerous flowers, and in others also in which abortion has 

 taken place of members of particular whorls. 



Pollen-grains. I — Prof. B. D. Halsted points out that pollen-grains 

 frequently alter their shape greatly when wetted. Oval grains may 

 increase as much as 33 • 2 per cent, in their shorter diameter, while 

 shrinking 12 • 2 per cent, in their longer diameter. Many grains have 

 characteristic folds which are lost when the grain is wetted. The pores 

 are not usually so evident in the dry pollen as when it is wet. For full 

 and perfect representation of a pollen-grain it should be measured twice ; 

 when dry, that is, in the condition to pass from the anther to the stigma, 

 and again when fully swollen by the imbibition of water. The largest 

 diameter measured was 130-138 ix, in (Enothera hiennis. 



Form of Pollen-grains. § — According to Herr F. Tschernich, the 

 morphological structure of the pollen-grain is sometimes uniform 

 throughout entire orders, as in the Coniferse, Graminefe, Compositfe, and 

 Caryophyllacefe. Tn other cases it can be used to determine the genus, 

 as in Salix and Populus among Salicaceae, Euphorbia, Buxus, and Crotdn 



* Bot. Gazette, xlv. (1889) pp. G7-9 (1 pi.). 



t Jahrb. f. Wiss. Bot. (Pringsheim), xx. (1889) pp. 349-426 (1 pi.). 

 X Bull. Torrey Bot. Club, xvi. (188i>) pp. 135-6. 



§ 'Ueb. d. Bedeutuug d. Pollens f. d. Charakteristik d. Pflanz n,' 1888. See 

 Pot" Centralbl., xxxviii. (18S9) p. 833. 



