Cavity closed by Andrmcium. 103 



the nectariferous annular disk at the hase of the flower. 

 Precisely similar is the structure of the nectar-cavity 

 in Gampamula persicifolia, G. pyramidalis, G. carpafica 

 G. spioata, G. trachelivmi, G. rapunml&ides, and G. iar- 

 bata, of which last I have given drawings (Plate III. 

 fig. 88, longitudinal section of flower ; fig. 89, a single 

 stamen, from the side turned towards the style). Here 

 again the filaments are much dUated towards their 

 base, and usually at the same time much bent, and 

 converted into scaly lamellae, which are concave on 

 the inner side so as to form an arch over the nectari- 

 ferous disk. As a rule, these dilated filaments are in 

 close contact with each other, and tolerably firmly set ; 

 so that an insect must have some strength to push 

 them apart. Moreover, their margins are often set 

 with trichomes, whereby the cavity is closed with still 

 greater security.-' 



The third mode of completely closing in the nectar- 

 cavity by means of the androecium is the crowding 

 together of the stamens. This occurs in very many 

 Mesembryanthacese and Oactacese, especially in Opuntia 

 and Mamillaria, and also in some Eosaceae and Amyg-. 

 dalese (Dryas, Potentilla, Geum, Persica). In Mamil- 



1 There are some Campanulaoese, however, e.g. Campanula 

 patula, where the vault formed over the nectariferous disk by the 

 dilated parts of the filaments is not completely closed. The fila- 

 ments are not in actual contact with each other laterally, but are 

 separated by chinks. These, however, are invariably guarded by a 

 thick investment of trichomes. 



