ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 661 



depends on internal causes, although influenced by adaptation to clima- 

 tic conditions. 



Conducting Apparatus of Nyctagineae.* — F. Gidon has studied the 

 structure and development of the conducting apparatus in the stem and 

 leaf in this order, and differs in several points from the conclusions of 

 Van Tieghem. The peripheral zone which gives birth to the so-called 

 supernumerary bundles is not a secondary generating zone ; it consti- 

 tutes in reality the procambium, which formed earlier the more deeply 

 placed bundles, and the apparent movement of which towards the 

 surface is due to the thickness of the non-vascular tissues which it 

 produces towards the interior, especially in the medullary rays. A 

 pericycle is always wanting. It is frequently replaced by a pseudo- 

 pericycle, the origin of which is complex ; it frequently arises from 

 the procambium or liber. Several other points of structure are noted 

 in the stem and leaves. The mesophyll may be entirely of a palisade 



character. 



C4) Structure of Org-ans. 



Fruit of the Scrophulariacese.f — A. Weberbauer gives an account of 

 the varieties in the anatomical structure and mode of opening in the 

 fruit of the Scrophulariaceae, including the Selagineae. A large number 

 are described in detail and classified. The capsule exhibits, in the 

 majority of the genera, the same kinds of imbibition movements that are 

 found in other families. They open with drought and close with moisture. 

 The opening is usually brought about by a movement or bending 

 outwards of the valves, less often by a bending inwards. There are 

 occasionally contrivances for assisting the transport of the fruit or of 

 the seeds by animals. 



Structure of Seeds.J — F. H. Billings has investigated the develop- 

 ment and structure of the seed of a large number of plants chiefly 

 belonging to the Gamopetalas (18 orders, 40 genera, 70 species), and 

 finds but few characters that can be used for purposes of general 

 classification. With the exception of the Primulaceaa and Plumbagineae, 

 there is only a single integument in the Gamopetalaa examined. When 

 the integument attains a considerable thickness, as is the case in all 

 the orders examined except the Oxalideas, Geraniaceae, and Plumbaginere, 

 it serves as a storing tissue for food-material. After impregnation the 

 integument increases in thickness, either from increase in size only 

 of the cells, or from increase in both size and number. The syner- 

 gids disappear, in almost all cases, soon after impregnation ; the anti- 

 podals are absorbed in the endosperm, taking no part in its formation. 



Where haustoria occur, they may often be characteristic even of 

 particular species. Their greatest activity is during the early stages 

 of the development of the seed. They contain one or more nuclei, 

 originating from the endosperm, except in the case of Calendula. 



Suckers of Sequoia sempervirens.§ — Suckers are of vary rare occur- 

 rence in Gymnosperms. Prof. G. J. Peirce describes those in Sequoia 



* Mem. Soc. Linn. Normandie, xx. (1900) pp. 1-120 (6 pis.). See Bull. Soc. Bot. 

 France, vii. (1900) p. 472. 



t Beih. z. Bot. Centralbl., x. (1901) pp. 393-157 (1 pi.). Cf. this Journal, 1898, 

 p. 319. X Flora, lxxxviii. (1901) pp. 253-318 (100 figs.). 



§ Proc. California Acad. Sci., ii. (1901) pp. 83-106 (1 pi.). 

 Dec. 18th, 1901 2 y 



