ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 329 



pollination embryos developed, and were proved to arise from the un- 

 fertilised oospheres. 



Di Candolle, Acgcstin — La parthenogenese chez les plantes d'apres les 

 travaux recents. [A review of recent work on parthenogenesis in plants, with some 

 general remarks.] Arch. Set. Phys. et Nat. Geneve, ex. (1905) pp. 259-72. 



•GuiGNARD, L. — La double fecondation chez les Malvacees. (Double fertilisation in 

 the Malvaceae.) 



[The author describes the details of the process of double nuclear fusion in 

 members of this order, especially Hibiscus Trionum.'] 



Jowrn. de Bot., 1904, pp. 296-308, figs, in text. 



Physiology. 

 Nutrition and Growth. 



Mechanical Adjustment in Cereus giganteus to Varying Quan- 

 tities of Stored Water.* — Effie S. Spalding has made a series of 

 measurements and observations at the Desert Laboratory in the 

 •Southern United States, to determine the relation of the fluted colum- 

 nar cactus type to varying amounts of water-storage. The strong ribs 

 and corresponding furrows suggest a ready adjustment by a bellows-like 

 action of the ribs and furrows to changes in bulk due to varying amounts 

 •of stored water. A cross-section of a stem of a giant cactus shows a 

 heavy band of thick-walled, sub-epidermal tissue, which is very strong 

 and elastic. Beneath this is a band of thin-walled chlorophyll cells, and 

 all the tissue between this and the ring of fibro- vascular bundles is made 

 up of thin-walled water-storing cells. The construction suggests that a 

 change in bulk corresponding to varying quantities of stored water could 

 hardly affect the central mechanical cylinder, but would probably mani- 

 fest itself externally by expansion or contraction of the circumference 

 effected by folding or unfolding of the ribs and furrows. These sug- 

 gestions were borne out by the results of experiment — changes in the 

 circumference were found to be accompanied by such action of the ribs, 

 and these movements are directly correlated with increase and decrease 

 in the amount of water supplied to the plant. Variations in the circum- 

 ference of the stem, due to changes of water-content, are not the same 

 •at all heights, but are least pronounced at the base and top. 



Study of Endotropic Mycorhiza.t — J. Gallaud begins with an his- 

 torical account of Mycorhiza generally, of its discovery, and of the 

 many papers that have been published on this much-debated subject. 

 He then gives an account of his own research on endotropic forms. He 

 •distinguishes four series or types : (1) The Arum series, in which the 

 roots are usually invaded by the fungus, though occasionally free. The 

 infected roots are more opaque, rigid, and hard ; they are bent and 

 twisted, and break more easily at those points where the hyphae are most 

 abundant. The mycelial filaments pierce the cells of the three outer 

 layers of the root ; they are intra-cellular. They then spread through 

 the intra-cellular spaces, but branches from the hyphaB pierce the cells 



• Bull. Torrey Bot. Club., xxxii. (1905) pp. 57-68 (2 pis. and 9 figs, in text). 

 t Kev. Gen. Bot., xvii. (19U5) pp. 5-48, 66-85 (4 pis.). 



