i8i8 A TEXTBOOK OF THEORETICAL BOTANY 



P. veitchii or Ampelopsis veitchii is the Ampelopsis Creeper which climbs 

 by suctorial discs (Fig. 1717). It also has red autumn foliage. 



GERANIALES 



The Geraniales are Archichlamydeae in which the flowers are bisexual, 

 actinomorphic or rarely zygomorphic. The floral parts are pentamerous 

 and cyclic. The sepals are imbricated in the bud, free or sometimes united 

 at the base, and may be persistent. The petals are imbricated in the bud, 

 but are always free. The stamens are arranged in two whorls, generally 

 consisting of five stamens, becomirg obdiplostemonous by abortion of the 

 outer whorl; or they may be numerous, when the filaments are either free 

 or united into a tube or ring at their base. The gynoecium consists of three 

 to five carpels, which form a plurilocular ovary. The ovules are axile in 

 attachment, pendulous and anatropous in form, with the micropyle directed 

 outwards. The ovules are provided with two integuments. 



The limits of this Order are very wide. According to Engler it includes 

 some twenty families, while both Wettstein and Rendle exclude the whole 

 of Engler's sub-order, Tricoccae, and regard the families included in it as 

 a separate order. Hutchinson on the other hand further splits up the order 

 as Engler conceived it. It is obvious that there is a considerable diversity 

 of form within the order, the more so when it is allowed to embrace the 

 large number of families included by Engler. On the other hand distri- 

 buting the families between three orders, Geraniales, Malpighiales and 

 Euphorbiales, as is done by Hutchinson, would be too elaborate a system 

 for us to adopt here. It seems therefore most convenient to follow Wettstein 

 in this matter. Under his system the Geraniales, or Gruinales, as he terms 

 them, include the following important families: Linaceae, Oxalidaceae, 

 Geraniaceae, Tropaeolaceae, Balsaminaceae, Erythroxylaceae, Malpighi- 

 aceae and Zygophyllaceae. 



Most of the plants are herbaceous, occasionally woody or climbers, 

 usually with simple, alternate leaves with or without stipules. The order 

 shows a gradual transition from actinomorphy to zygomorphy. 



We shall consider the family Geraniaceae in detail but before doing so 

 we may refer briefly to some of the more important features exhibited by 

 the other families. 



The Linaceae are a small family of some 150 species, the majority of 

 which belong to the genus Linum. Most of the species are herbs or small 

 shrubs with small entire, alternate leaves often provided with stipules. In 

 the genus Limun (Fig. 17 18) are some ninety-five species, four of which 

 occur in Britain. L. catharticum, the Purging Flax, is an annual which 

 extends to Arctic Europe; L. usitatissimum, the Common Flax, which is 

 native of the country between the Persian Gulf, the Caspian Sea and the 

 Black Sea; L. perenne (Fig. 1719), the Blue Flax; L. angiistifoUum and 

 L. grandiflorum which is cultivated in gardens. The seeds have a mucila- 

 ginous testa, which swells on wetting and yields an oil on pressure which 



