266 BRITISH FLOWERING PLANTS chap. 



of fungus mycelium, by means of whicli the plant is 

 able to feed on the nutritive matter in the humus. 

 It is a case, therefore, of a flowering plant living at the 

 expense of a fungus, reversing the usual rule. Prob- 

 ably, however, the fungus also derives some advantage 

 from its association with the Monotropa. The terminal 

 flower is in fives, the rest are in fours ; the former, 

 according to Kirchner, having 10, the others 8 nec- 

 taries at the base of the ovary, which project into 

 corresponding hollows in the corolla. The anthers open 

 transversely. The style is hairy, which tends to pre- 

 vent the pollen from reaching the stigma of the same 

 flower. 



PEIMULACEJE 



The flowers in this beautiful family ofi'er considerable 

 variety in their arrangement. The corolla, indeed, is in 

 all cases the invitation to the feast. Some, however, 

 are merely pollen flowers, though the majority secrete 

 honey. Samolus has a " sham " nectary. In some 

 species the honey is accessible to bees with a short 

 proboscis, in others only to those with a long one, while 

 there are some — Primula farinosa, for instance — which 

 are adapted to Lepidoptera. Many species of Primula 

 and Hottonia are dimorphous. The flowers of some 

 species are upright and apparently unprotected, but the 

 mouth is narrow, so that rain-drops cannot enter, but 

 roll ofi" the surface. 



Primula 



Honey is secreted by the base of the ovary. The 

 capsule dehisces by ten valves. The outer epidermis is 

 passive ; the cells within are lignified and contract on dry- 

 ing, while the inner epidermis forms the layer of resistance 

 (Fig. 167). At the lines of fissure the inner epidermis 

 only is lignified, while elsewhere this is the case with 

 the whole of the inner tissue. We have four species. 



