602 hydeochaeidacejE — oechidace^. 



celled ; ovules 00, anatropal, frequently attached to parietal placentas; 

 stigmas 3-6. Fruit dry or succulent, indehiscent, uni- or multi-locu- 

 lar. Seeds numerous, exalbuminous ; embryo straight, radicle remote 

 from the hilum. — Floating or aquatic plants, with parallel-veined 

 leaves, sometimes spiny. Chiefly found in Europe, Asia, North 

 America, and Australia. The plants of this order are not remark- 

 able for their properties. Some are mucilaginous and astringent.^ 

 Vallisneria spiralis (figs. 249, p. 173; 513, p. 283) is a, dioecious 

 plant, the male flowers of which, at the time of flowering, are 

 detached from the mud of the water in which they grow, and 

 float on the surface. At the same time the female flower develops 

 a long spiral peduncle, by means of which it reaches the surface 

 of the water, so as to allow the application of the pollen (p. 283). 

 Vallisneria and Anacharis exhibit under the microscope the rotation 

 of protoplasm in their cells. The order has been divided into two 

 tribes : — 1. Vallisneriese, ovary 1 -celled. 2. Stratiotese, ovary many- 

 ceUed. There are 10 known genera, according to authors, including 

 20 species. Examples — Vallisneria, Udora, Anacharis (Elodea), Stra- 

 tiotes, Hydrocharis. 



Order 186. — Orchid acb^, the Orchis Family. [Mono-Epigyn) 

 Flowers bisexual. Perianth adherent, herbaceous, or coloured, with 

 a 6-partite limb (fig. 846 pe, pi), the segments being arranged in 2 

 rows ; exterior row (fig. 845 ce), called the calyx (although Lindley 

 says it is more properly the corolla, the true calyx or calyculus being 

 usually abortive), consisting of 3 segments (rarely 2 by adhesion), the 

 odd one of which is often next the axis by a twisting of the ovary ; 

 interior row (fig. 845 ci), called the corolla (regarded by Lindley as 

 petaloid stamens), consisting usually of 3 segments (very rarely 1), the 

 odd one of which is called the labeUum or lip (fig. 317, p. 205). This 

 labeUum (figs. 845, 846, 847 I) frequently dififers from the other divi- 

 sions of the perianth, assuming remarkable forms, being lobed, spurred 

 at the base, or furnished with peculiar appendages, which are some- 

 times derived from the stigma. It is sometimes divided by contrac- 

 tion, so as to exhibit three distinct portions, the lowest being the 

 hypochUium {w6, under, and %£/Xo?, lip) ; the middle, the mesochUium 

 (/iEtfos, middle) ; and the upper, the epichilium i\m, upon or above). 

 Stamens 3, epigynous, united in a central column along with the 

 style ; the two lateral stamens are usually abortive (fig. 846 ss), the 

 central one opposite the odd exterior segment being fertile (fig. 846 e) ; 

 but at times the two lateral are fertile, and the central one is abortive ; 

 anthers 1-2-4-celled (fig. 848) ; pollen powdery or cohering in definite 

 (fig. 854) or indefinite waxy masses (poUinia) (figs. 849, 853 ; 387, 

 p. 230), which often adhere by a caudicle (fig. 853 c) to a gland con- 

 nected with the beak (rostellum) of the stigma. This gland is some- 

 times naked, at other times in a sac or pouch (bursicula). Ovary 



