ANGIOSPEUMvE, DICOTYLEDONES. 755 



Mistletoe ( Viscum alburn, found in Scandinavia as far north as 59° 30') and several 

 species of the genus Thesium reach furthest north. Thesium alpinum attains its 

 highest limit in the Alps at 2400 metres. Fossil remains occur in the strata of the 

 Tertiary Pei'iod. The number of existing species is about 750. 



Alliance XXXIX.— Rafflesiales. 



Families: EafflesiacecB, Apodanthacece, and Gyhnacece. 



Plants destitute of chlorophyll, parasitic on the roots of green-leaved woody 

 plants. Flowering axis greatly thickened, fleshy. Flowers solitary or in racemes, 

 hermaphrodite or pseudo-hermaphrodite. Perianth 4-6 partite. Ovary inferior. 

 The cavity of the ovary is divided irregularly into chambers which are tilled with 

 strands and ridges bearing the ovules. Above the ovary rises a columnar style 

 with a discoid thickening at the top, and upon the under margin of this disc the 

 stigmatic tissue is situated. The stamens are inserted underneath the stigmatic 

 tissue in a circle. The fruit is fleshy, baccate, and crowned by the persistent 

 column. The seeds have hard coats. The embryo consists of few cells, has no 

 cotyledons, and is surrounded by an oily endosperm. For a description of the 

 suction-organs see vol. i. pp. 199-204, and for the size of the flowers see vol. ii. 

 p. 185. The Rafflesiales live in the ti-opical and sub-tropical regions of both the 

 Old and the New World; two species of the genus Cytinus (see vol. i. p. 201) belong 

 to the Mediterranean flora. No fossil remains are known. The number of extant 

 species hitherto identified is 29. 



Alliance XL. — Asarales. 

 Families: Aristolochiacece, Asaracece. 



Perennial plants, some with subterranean tuberous or creeping rhizomes, some 

 with twining liane-like stems (see vol. i. fig. 95 \ p. 364). Foliage-leaves broad, with 

 entire margins, sometimes lobed. Venation apical (see vol. i. p. 633). Flowers 

 hermaphrodite, solitary, or in cymose inflorescences, especially in axillary fascicles. 

 Perianth of 3 petaloid leaves, united at the base. Gynasceum 4-6 carpellary; ovary 

 inferior or semi-inferior. Styles united into a column bearing a radiating stigma. 

 Androicium composed of 2-12 whorls of 3 stamens each. Ovules numerous in the 

 loculi of the ovary. Fruit a capsule (see p. 431, fig. 325'). The seed contains an 

 abundant endosperm, and a very small embryo with two cotyledons. 



The perianth in Asaraceae is actinomorphic (see p. 279, fig. 279 '^> ^'), whilst in 

 Aristolochiaceae it is zygomorphic or else unsymmotrical, and the tube of the peri- 

 anth is variously curved and inflated (.see p. 166, fig. 242, and p. 226, fig. 257 ''•'•*• "). 

 These flowers are very striking, on account not only of their form, but also of 

 their dark-browTi colour; moreover, in many cases they attain to an extraordinary 

 size. Mention has already been made of Aristolochia gifjas (see p. 1S5), and 

 recently a Birthwort (Aristolochia Goldeana) has been found in West Africa whicli 



