1942 A TEXTBOOK OF THEORETICAL BOTANY 



anaceae and Adoxaceae are included in the Rubiales. Eichler places Adoxa 

 in the Caprifoliaceae while other workers have suggested that it has a 

 relationship with the Saxifragaceae or the Araliaceae. 



We shall first refer briefly to the families Adoxaceae, Valerianaceae and 

 Dipsacaceae and then consider the great family of the Compositae in some 

 detail. 



The Adoxaceae contain the single species Adoxa moschatellina 

 which is a small herb arising from a perennial rhizome. The radical 

 leaves are ternately divided and the flowering stalk bears one pair of similar 

 leaves. At the apex of the stalk is a head of five small, greenish-white, 

 hermaphrodite flowers. The terminal flower is usually tetramerous while 

 the other four are pentamerous. The calyx is formed of three sepals, while 

 the corolla comprises usually five small petals. The stamens, which may 

 number four, five or six, appear to be double owing to a split which begins 

 near the base, so that each bears half an anther. The ovary is more or less 

 inferior and contains four or five loculi with a single pendulous ovule in 

 each loculus. The short styles are equal in number to the loculi. The fruit 

 is a drupe and the seeds contain minute embryos embedded in endosperm. 



The flowers are pollinated by small insects which are attracted by the 

 musky smell and by nectar which is secreted around the base of the stamens. 



As has already been pointed out the position of Adoxa is somewhat 

 dubious and it is placed here mainly on account of the single pendulous 

 ovule in each loculus. The plant is widely distributed over north temperate 

 regions and is not uncommon in Britain, 



The Valerianaceae comprise some ten genera and nearly 400 species 

 which occur mostly in north temperate regions. The plants are very rare 

 in Africa and absent from Australia. Most of the species are herbs though 

 a few are shrubby, with opposite leaves and small flowers in cymose 

 inflorescences. Valeriana (Fig. 1870), Valerianella and Centranthus are 

 found in Britain. Centranthus ruber (Fig. 1871) is really an escape from 

 cultivation for its home appears to be the Mediterranean region. It has how- 

 ever for long become naturalized on old walls. It may be found in three 

 forms, one deep red, one white and, by far the most common, one pink. 

 Valerianella olitoria (Lamb's Lettuce) is used in salads, while Spikenard, 

 one of the most prized perfumes of antiquity, was prepared from the young 

 shoots of Nardostachys jatamansi, a native of the Himalayas. 



The flowers may be hermaphrodite or unisexual and somewhat zygo- 

 morphic. The calyx is represented by an epigynous ring. The corolla is 

 tubular, often saccate at the base; the stamens in the corolla tube alternate 

 with the lobes and vary between one and four. The ovary is inferior and 

 made up of three united carpels though only one loculus is fertile and 

 contains a single pendulous ovule. The fruit is dry, indehiscent and one- 

 seeded. The embryo is straight and possesses no endosperm. 



The pollination mechanism is elaborate and may even extend to a 

 condition of dimorphism. The small flowers, rather inconspicuous 

 separately, are aggregated into large heads. Each flower possesses nectar 



