THE ANGIOSPERMAE 



1187 



they ripen are brought into the appropriate position for meeting insect 

 visitors. Well-known examples are Tropaeolum speciosum, Dictamnus 

 fraxinella, Gloriosa siiperba, and Parnassia pahistris. The stamens in many 

 flowers, e.g., in IVIyrtaceae, Rosaceae, Umbelliferae and Urticaceae, are all 

 incurved at first, with the anthers clustered around the base of the style, or 

 even, as in some Melastomaceae, held in pockets formed by the receptacle. 

 An epinastic movement, due to increased growth on the adaxial side of the 

 filament, causes them to straighten out and raise up -the anthers, after the 

 perianth has expanded. The straightening movement of the filaments in 

 the Urticaceae is one of elasticity, not of growth, and is correspondingly 

 sudden and explosive, the anthers being flung outwards over the edge of the 

 perianth and a cloud of the dry pollen discharged. The well-known carpet- 

 ing plant, Pilea elegans, has gained the name of " Artillery Plant " for this 

 behaviour. 



The specialized forms assumed by stamens are almost indefinitely 

 variable and quite beyond detailed description. A few selected examples 

 are shown in Figs. 1 160 and 1 161. Peculiarity of form is often directly asso- 

 ciated with the requirements of pollination, but by no means always, and is 



12 



13 



14 



An 



* 



Fig. 1 160. — Various types of stamens, {i) Cyclanthera. {2) Cucuniis. (t,) Lour us. {^) Portu- 

 laca. (^) Burmannin. {b) Hydrolea. {-;) Schizaudra. (8) Vinca. (g) Asclepias. (10) Ste- 

 phania. (11) Tacca. (12) Viscuvi. (13) Carpinus. (14) Hypoxis. (15) Barbacenia, 

 (After Le Maout and Decaisne.) 



