THE DICOTYLEDOXES 1907 



commercial nicotine. A', ajfinis and others are used as half-hardy annuals in 

 garden bedding. The common flower colours are red and white. The 

 flowers are night-scented and secrete nectar. When they open (Fig. 1826) 

 the stigma is mature and the anthers dehisce at the same time or later. 

 The stamens differ in length in the various species, but there are usually 

 four stamens of the same length and one, the posterior, which is shorter. 

 Occasionally two are higher than and tw^o at the same level as the style. 

 Cross-pollination is sometimes effected by night-flying moths, particularly 

 in the white form of A', ajfinis. In N. tahacum self-pollination generally 

 occurs though bees have been observed to visit the flowers occasionally. 



Species of the genus Salpiglossis are cultivated as half-hardy annuals 

 in gardens for the sake of the large flowers bright with coloured markings. 

 There are eight South American species. The genus Schizanthus (Fig. 1827) 

 also provides cultivated species often grown for decoration in green- 

 houses or as a summer annual. There are eleven species all found in Chile. 



The genus Cestrum with about 150 species occurs in America; some are 

 grown as wall-shrubs in gardens, but they are usually treated as greenhouse 

 subjects. 



Personales 



As already explained, this order is used by Bentham and Hooker and by 

 Hutchinson to include the following families: Scrophulariaceae, Oro- 

 banchaceae, Lentibulariaceae, Gesneriaceae, Bignoniaceae, Acanthaceae 

 and the less important order Pedaliaceae in which are included several 

 species whose fruits we have already mentioned. (See p. 1565.) 



The order may be characterized by the alternate or opposite leaves, 

 the invariably zygomorphic corolla, the reduction in the number of stamens 

 to four or two. The ovary contains numerous ovules, which generally 

 have axile placentation. 



The order includes a number of important families, as will be seen from 

 the above list, and though we shall consider only the Scrophulariaceae in 

 detail we shall first consider more briefly the important features of the other 

 families. 



The Orobanchaceae are all parasites living usually on the roots or 

 stems of Angiosperms (Fig. 1828). The leaves are alternate and are never 

 green. They are reduced to fleshy scales at the base of the stem and may 

 be greatly reduced in the flower spike. The flowers are solitary in the axils 

 of bracts and form large racemose inflorescences. The flowers are strongly 

 zygomorphic, hermaphrodite and dusky vellow or violet in colour. The 

 androecium consists of four stamens, in two pairs, of which the anterior is 

 longer. The ovary is superior and unilocular, with four parietal placentae 

 which bear numerous ovules. The seeds are very small, but are endo- 

 spermic and contain minute embryos. Pollination is by insects which are 

 attracted by nectar secreted at the base of the flower. 



The species are almost confined to the northern hemisphere and are 

 most plentiful in the warmer parts of Europe and Africa. About a dozen 



