372 



SYSTEMATIC BOTANY. 



fication, as mentioned under those Orders; the Apostasiaceas have 2 

 stamens only, with their filaments adhering to the lower part of the style. 

 The ovary is apparently formed of 3 carpels, with the stigmas simple. 

 Since they alternate with the placentas, Lindley supposes the ovary to be 

 formed of 6 carpels, 3 fertile and 3 barren ; but this seems contrary to 

 analogy and without sufficient independent support. In Apostasiacete, 

 Marantacese, and Zingiberaceae the ovary is 3-celled, or sometimes imper- 

 fectly so in the last, from the margins not meeting in the centre. Seleni- 

 pedimn has a 3-celled ovary. The seeds, which are very minute, are of 

 simple organization : the ovules, at the time of fertilization, consist solely 

 of an embryo-sac with 2 integuments ; and the ripe seed presents an embryo 

 devoid of distinct organs (cotyledon and radicle), enclosed in a loose testa 

 in this respect exhibiting a relationship to Burmamriaceae. 



Fig. 461. 



Fig. 461. Orchid flower, showing the parts of the perianth and column. 



Pig. 462. Flower of Drakea : the parts of the perianth are turned back to show the column 

 and the lip, which is jointed in the middle, and endowed with hinge-like 

 motion when irritated ; so that an insect alighting on it is entrapped, and in its 

 struggles to escape removes the pollen-massses. 



The labeUum sometimes exhibits irritability, moving spontaneously or 

 when touched (Megaclinium^ Bolbophyllum, Drakea, &c.) (fig. 462) : its 

 forms are most varied and strange, often causing the entire flower to re- 

 semble an insect or some other living object. The rostellum and stalk of the 

 pollen-masses are also endowed with contractile properties. In Catasetum 

 these are so powerful as to cause the sudden forcible ejection of the pollen- 

 masses from the anther-cells, when the rostellum or other sensitive organ 

 is touched, as by the proboscis of an insect. Insects visiting the flowers 

 of our common English Orchis, for the sake of the honey, come into contact 



