ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 385 



liave no power of turgidity, performing the function of receptacles for 

 water. 



In dicotyledons the medullary rays are also connected with the 

 vessels by pores, which sometimes attain a very great size. The 

 woody parenchyma and medullary rays stand in a close relationship 

 with the vessels, and together furnish a channel for the transport of 

 solutions of organic compounds ; the sap is conducted through the 

 former, while the vessels serve as reservoirs to which the former give 

 up their superfluous sap, and take it up again from them when 

 wanted. 



Diagnostic Value of the Number and Height of the Medullary 

 Rays in Conifers.* — B. Essner points out that these characters cannot 

 be used for the determination of the species of fossil coniferous woods, 

 as has been proposed, since both the number and height of the 

 medullary rays are subject to considerable variation in the same species 

 according to age ; they are most numerous in the first annual ring, 

 then decrease, and subsequently again increase. Their height increases 

 regularly with their age. 



Achenial Hairs and Fibres of Compositae.t — G. Macloskie 

 describes the peculiar hairs attached to the achenes of many Com- 

 positse. Duplex hairs are characteristic of the families Asteroideee, 

 Eupatoriese, Vernoniese, Helianthoideas, HelenioidcEe, Arctotidese, and 

 Mutisiese ; but do not occur in Anthemideae or Cichorieae. Each hair 

 consists of two tubes with a partition between, like the two flues 

 of a double chimney ; they contain special fibres or elaters which are 

 rapidly uncovered on access of moisture, swelling and escaping by 

 the tips of the tubes, as by the lifting of a pair of trap-doors. There 

 are also similar fibres contained in superficial cells of the pericarp in 

 Cichorieae, which aid in the dehiscence of the seed-vessel (generally 

 described as indehiscent), and the pressing out of the seed. 



Crystals of Calcium oxalate in the Cell-wall.J — Crystals of 

 calcium oxalate in the cell- wall have hitherto been observed in 

 Mesembryanthemum, Sempervivum, Dracmia, Araucaria, Welwitschia, 

 and Ephedra. H. Molisch records an additional instance in Niiphar 

 and NympJicea. They occur especially in the walls of the well-known 

 stellate hairs of the fundamental parenchyma which surrounds the 

 intercellular spaces of the leaf and leaf-stalk. The crystals vary 

 greatly in size from all but invisible points to 6 • 6 /a in length. 



Influence of Sunny and Shaded Localities on the Development 

 of Leaves.§ — Haberlandt, in an examination of the comparative 

 anatomy of the assimilating tissues in plants, came to the con- 

 clusion that light is almost without influence in governing the shape 

 of leaves or the arrangement of the chlorophyll-cells. On the other 



* Abhandl. Naturf. Ges. Halle, xvi. (1882). See Bot. Centralbl , xii. (1SS2) 

 p. 407. 



t Amer. "Natural., xvii. (If^SS) pp. 31-6. 



t Oesterr. Bot. Zeitschr., xxxii. (1882) pp. 382-5. 



§ Jen. Zeitschr. f. Naturwiss., ix. (1882) pp. 162-200 (1 pi.). See Amer. Joura. 

 Sci., XXV. (1883) pp. 313-4. Cf. this Journal, ii. (1882) pp. 368, 373; aijte p. 92. 

 Ser. 2.— Vol. III. 2 C 



