142 Transactions of the Society. 



the surface of the capsule, and exposing them to the action of 

 wind. 



In some species the ovules are undeveloped or very rudimentary 

 when the plant is in flower. According to Hildebrancl, in Den- 

 drobium the formation of the ovules has not yet commenced, even 

 the placentae are not fully developed, and it is not till four months 

 after the deposition of the pollen that the formation of the embryo 

 begins. 



Iride.e. — The flower, is superior, with six petal-like leaves. 

 The ovary is inferior, 3-celled, with many ovules. 



The order is a large one, comprising 700 or more species, 

 inhabiting especially South Africa and other dry, sunny climates. 

 Five genera and six species only are truly British, four others 

 being more or less naturalised. 



The fruit is a capsule, bursting from the apex to the base into 

 three valves, along the line of the dorsal suture. Each cell may 

 contain few or many seeds, superposed in a double row. The seeds 

 of our British species are relatively large, but differ considerably in 

 this respect. They may be globose, angled, flattened, and some- 

 times winged. At least two types may occur in the same genus. 

 The embryo is small. 



Iris. — We have two species, 7. fcetidissima, the Blue, and 

 /. Pseudacorus, the Yellow Flag. 



The seeds of the former are large, globular, smooth, glossy, and 

 rich orange-red, or even scarlet. The bright colour, perhaps,, 

 deceives birds into the belief that they are sweet, and may thus 

 assist in their dissemination. The testa is fleshy. 



Fig. 24. — Seed of Drosera rotundifolia. x 20. 



The seeds of I. Pseudacorus are yellowish-red or brown ; more 

 numerous, much flattened by mutual pressure, when young and 

 soft. The testa is less spongy than in I. fojtidissima. 



The seeds of Gladiolus illyricus have a narrow wing. In G. 

 communis it is broader. The capsule opens at the upper end and 

 the seeds are jerked out. Perhaps their bright colour may assist 

 in their dispersal by birds. 



Dioscoeide^;. — The flowers are unisexual, with a perianth of 

 six divisions. The stamens are also six in number. The ovary is 

 inferior, 3-celled, and with one to three ovules in each cell. Styles 

 or stigmas, three. The embryo is minute, and the albumen hard. 



The order includes eight genera, with about 200 species, mostly 

 inhabitants of hot countries. The fruits are baccate in about half 

 the species, and capsular in the other half. The seeds are globose,, 

 or flattened, and even winged, as in Dioscorea. 



Two species only are European. 



