DICOTYLEDONS. 633 



Order 10. Gynandrae. The entire flower zygomorphic in origin and de- 

 velopment; by the torsion of the long inferior ovary (i) the anterior side of the 

 mature flower usually becomes posterior; both of the trimerous perianth-whorls 

 petaloid, the posterior leaf of the inner one (the labellum) generally provided 

 with a spur ; of the six typical stamens of the two whorls only the anterior ones 

 are eventually developed, and in (i) (with the exception of Cypripedium) the 

 anterior one of the outer whorl is alone fertile and has large anthers, the two 

 anterior ones of the inner whorl forming small staminodes ; but in Cypripedium it 

 is these latter that are fertile, the anterior one of the outer whorl forming a large 

 staminode ; in (2) the same occurs, or the three anterior ones are fertile ; filaments 

 of the fertile and sterile stamens coherent with the three styles into a gynostemium ; 

 pollen in single grains, tetrads, masses, or pollinia ; ovary inferior and unilocular 

 with parietal placentation (i) or trilocular with axile placentation (2) ; ovules 

 anatropous; seeds very numerous, very small, without endosperm, and with the 

 embryo undiff"erentiated. Small herbs or larger shrubby plants ; the tropical 

 Orchideae often epiphytal and furnished with peculiar aerial roots; our native 

 species perennial with underground rhizomes or tubers ; some Orchideae are 

 saprophytes destitute of chlorophyll, and a few have even no roots {Epipogium^ 

 Corallorhiza). 



Families: i. Orchideae. 



2. Apostasiaceae. 



The BurmanniacesB with cymose inflorescence, three or six fertile epipetalous 

 stamens, free tripartite style, and uni- or tri-locular inferior ovary, are allied to the 

 Gynandrae by their small seeds without endosperm and their undifferentiated 

 embryo ; and in this order, which consists for the most part of small plants, there 

 are some saprophytes destitute of chlorophyll. 



CLASS XIL 



DICOTYLEDONS. 



The ripe Seed of Dicotyledons contains either a large endosperm and a small 

 embryo (as in Euphorbiaceae, Coffea, Myrtstica, Umbelliferae, Ampelideae, Polygon- 

 aceas, Csesalpinese, &c.) ; or the embryo is comparatively large, and the endosperm 

 occupies but a small space {e.g. Plumbagineae, Labiatse, Asclepiadeae, &c.); or, 

 thirdly, the endosperm is entirely wanting, and the embryo fills up the whole of the 

 space enclosed by the testa, and thus, when ripe, often attains a very considerable 

 size {e.g. ^s cuius, Juglans, Cucurbita, Tropceolum, CupuHferae, Leguminosae, &c.); 

 though in small seeds it still remains of moderate dimensions (as in Cruciferae, Com- 

 positae, Rosiflorae, &c.). The absence of endosperm generally results from its 

 absorption by the rapid growth of the embryo before the ripening of the seed; 

 only in a very few cases is it rudimentary from the first {Tropceolum, Trapd). In 

 most of the Nymphaeaceae and in the Piperacese the embryo and the endosperm 

 which surrounds it both remain small, the rest of the space within the testa being 

 occupied by perisperm. 



