ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 79 



By the growth of the seed the chalazal region is forced into a lateral 

 position. The antipodals disappear, and the chalazal end of the embryo- 

 sac formerly occupied by them is now filled with endosperm-cells pro- 

 jecting into the chalazal tissue. There seems to be no doubt that this 

 is a provision for increasing the absorbing surface of the endosperm in 

 the region of greatest food-supply. Similar arrangements have been 

 observed in other plants. 



Fruit of (Enanthe.* — M. J. Briquet has paid special attention to the 

 fruit of this genus of Unibelliferse. The chlorophyll disappears very 

 early from the outer layer of the mesocarp. The conducting bundles- 

 serve chiefly for the supply, not for the elimination of assimilated sub- 

 stance. The oil-glands are regarded by the author as a means of pro- 

 tection against fructivorous or seminivorous birds. The fruit has a. 

 beautiful apparatus for allowing it to swim for weeks upon the water, in 

 the form of groups of aeriferous cells imbedded in the mericarp. 



Dehiscence of the Nutmeg.f — M. J. N. Janse attributes the bursting 

 of the fruit of Myristica to the co-operation of three forces : — a mutual 

 tension between the kernel and the shell ; the development of a special 

 portion of the pericarp into an " expansion-tissue " ; and a tension 

 within the shell itself. M. Janse supports the view that the purpose of 

 the bright-coloured aril or mace is the attraction of birds which feed 

 upon it, and pass the seeds unharmed in their excrement. 



Biastrepsis in its relation to Cultivation.^ — Using the term " bia- 

 strepsis," as proposed by Schimper, as an equivalent for the German 

 Zwangsdrehung (often rendered " twisting of the stem ") M. Hugo de 

 Tries states, as a general rule, that the jnienonieaon (especially in the 

 case of Dipsacus sylcestris) is in a high degree dependent on the con- 

 ditions which obtain during and subsequently to the germination of the 

 seed. Conditions which favour the vigorous development of the plants 

 promote also the size and the number of the portions of the main stem, 

 and of the branches which show the twisting. Biastrepsis occurs only 

 in plants the shoots of which have opposite or whorled leaves ; the 

 phyllotaxis becomes spiral instead of verticillate, the successive leaves 

 of the spiral being connected by their bases. 



Stem of Aristolochia.§ — Herr H. C. Schellenberg has studied the 

 structure of the abnormal stem of Aristolochia siplw, and is of opinion 

 that the main object of the mechanical ring is the increase of its flexi- 

 bility rather than the protection of the sieve-tubes. In the twining 

 species of Aristolochia the pith and medullary rays are composed of 

 unlignified thin-walled cells ; while in the erect species these cells are 

 thick-walled and lignified. A. siplw possesses no special climbing con- 

 trivances during its firtt year of growth. 



Floating-Apparatus of the Leaves of Pistia.]] — Prof. T. Ito de- 

 scribes the peculiar floating-apparatus in the leaves of Pistia stratiotes, an 

 aquatic Aroid. A little above the base the leaf is swollen into an obovate 



* Bull. Herb. Boisbier, vii. (1899) pp. 467-88 (11 figs.), 

 t Ann. Jard. Bot. Buitenzorg, xvi. (1899) pp. 17-45 (1 pi.)- 

 % Ann. of Bot., xiii. (1899) pp. 395-420. 



§ Festschr. f. Schweudener, 1899, p. 301 (1 pi.). See Beiheft z. Bot. Centralbl., 

 ix. (1899) p. 16. || Ann. of Bot., xiii. (1899) p. 466. 



