ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 411 



and resemble much more closely the Gesneriacese. The Utriculariaceaa 

 are a well-defined group. 



The haustoria of the Orobancheas and EhinanthacesB * are interesting 

 from a morphological point of view. They are usually thallomes which 

 develope above the surface on normal roots ; the most simple resemble 

 hairs, the more complicated have a central irregular bundle of xylem 

 and phloem ; and they may then assume the function of roots. They 

 may become so closely united with the root of the host, that xylem 

 unites with xylem, phloem with phloem, parenchyme with parenchyme. 

 This is in consequence of the meristem, when it enters the root of the 

 host, developing xylem centripetally from the spot where it comes in 

 contact with the xylem of the host ; this again determining the position 

 of the other tissues. 



Anatomy of Bromeliaceae.t — M. A. De Wevre briefly describes the 

 main points in the anatomy of this natural order, derived from the 

 examination of a large number of species. 



The most conspicuous character, and a universal one without excep- 

 tion, is the presence of scale-hairs on the leaves. Each hair consists of 

 a plate, a single cell in thickness, borne on a central pluricellular stalk ; 

 their form varies greatly; and it is their presence that gives the 

 characteristic silvery appearance to the leaves of bromeliads. In a few 

 species they are found only on the lower part of the leaf. Similar hairs 

 occur nowhere else among Monocotyledons, except in a few palms, 

 where they are deciduous. 



There is never in the leaves a well-developed layer of palisade-cells ; 

 but in some species the outer cells of the mesophyll are slightly longer 

 than the others. The stomates are arranged in rows, separated by bands 

 of tissue from which they are absent. The guard-cells are always four 

 in number, of which two are parallel to the pore, and two perpendicular 

 to it. All Bromeliacea3 are distinguished by the presence of an aquifer- 

 ous hypoderm, which occurs also in Palmse, Pandauaceas, some Amaryl- 

 lidese, &c. In Ananassa macrodosa and some other species it constitutes 

 nearly three-fourths of the thickness of the leaf. The cells of which it 

 is composed are sometimes polygonal, sometimes elongated, sometimes 

 of both forms. A tangential section always shows the epidermal cells 

 with undulating walls; these cells have generally thick walls, the 

 thickening being sometimes on the outer, sometimes on the inner wall. 



The fibrovascular bundles which run through the whole length of 

 the leaf are usually very numerous, and are collateral in structure, 

 generally surrounded by a very strong sclerotized sheath, especially in 

 the species with long leaves. As in most Monocotyledons, oxalate of 

 lime occurs in the form of raphides, rarely in that of prisms {Caraguata 

 Zalinii). 



B. Physiology. J 

 (1) Reproduction and Q-ermination. 



Fertilization of Amorphophallus Rivieri.§ — Sig. E. Pirotta has 

 determined that the pollination of this species of Aroidese is effected by 



* Cf. this Journal, 1888, p. 80. 



t Bull. Soc. E. Bot. Belg., xxvii. part 2, 1887 (1889) pp. 103-6. 



X This subdivision contains (1) Reproduction and Germination; (2) Nutrition 

 and Growth (including Movements of Fluids) ; (3) Irritability ; and (4) Chemical 

 Changes (including Respiration and Fermentation). 



§ Nuov. Giorn. Bot. Ital., xxi. (1889) pp. 156-7. 



