506 DICOTYLEDONES. 



A. Pentacyclicae. 

 Family 26. Bicornes. 



This family is chiefly composed of shrubs, less frequently of 

 small trees, or perennial herbs; their leaves are undivided, most fre- 

 quently evergreen, stiff and leathery, and always without stipules. 

 The flowers are $ and regular, rarely slightly. zygomorphic, most 

 frequently obdiplostemonous, and 4- or 5-merous through all the 

 5 whorls. The stamens are attached to the receptacle, and as a rule 

 are quite free from the petals, an attachment which is very rare 

 among the Gamopetalae. They have a simple gynceceum with one 

 undivided style, a commissural stigma, and a multilocular ovary, 

 whose axile placentae project considerably into the loculi, and bear 

 a large number of ovules. The placentas are sometimes not united, and 

 in consequence, the ovary is 1-locular with incomplete partition-walls, e.g. 

 Pyrola, Monotropa. Embryo straight, with endosperm. The carpels 

 are placed opposite the petals. 



The diagram is generally Sn, Pn, An + n, Gn, in which n is 4 

 or 5. To this may be added, that the corolla is in 'most cases ganio- 

 petalous, but in some (especially Pyrolacese) perfectly polypetalous ; 

 and that the anthers usually open by pores, and often have two horn- 

 like appendages (hence the name " Bicornes ") (Figs. 545, 546) ; 

 frequently the two halves of the anther are also widely separated 

 from each other at the upper end, so that the pores are placed each 

 one at the end of its own tube (Fig. 546) ; the pollen-grains in 

 the majority are united into tetrads (Fig. 542 D). The flowers, as 

 a rule, are pendulous and borne in racemes, coloured (red or 

 white), but odourless. When the fruit is a capsule, the placenta 

 with the seeds attached persists as a central column. A mycorhiza 

 occurs on many. 



The majority of plants belonging to this family inhabit cold 

 and temperate countries, or high mountains in tropical regions ; 

 they prefer cold and dry or damp places (bogs, heaths, etc.). 

 Plentiful in N. America. 



Order 1. Pyrolaceae. Perennial herbs ; petals most frequently 

 quite free from each other, and falling off singly after flowering ; 

 the anthers are without appendages, and open by pores (Fig. 544), 

 or by a transverse slit. The placentae are thick. The seeds in 

 the capsule-like fruit (loculicidal dehiscence) are exceedingly small 

 and light, they have a sac-like testa which loosely envelops them, 

 an oily endosperm, and an extremely simple embryo, which consists 



