i886 A TEXTBOOK OF THEORETICAL BOTANY 



introduced into the slits which lead to the stigmas, cross-pollination is 

 effected and another clip becomes attached as the bee leaves. It has been 

 proved that self-pollination is impossible, for pollen is completely infertile 

 on the stigmas of the same flower or even on plants raised vegetatively 

 from the same stock. 



A. ciirassavica is pollinated by butterflies, the clips becoming attached 

 to the feet. Miiller depicts an insect with as many as eleven clips and eight 

 pollinia attached to a single limb. 



The genus Stapelia has also a similar pinch-trap mechanism, and emits 

 a carrion odour attactive to flies, which effect cross-pollination by means of 

 their probosces. Cleistogamy is said to occur in this genus. 



Other well-known genera of this family with clip pollination mechanisms 

 are Ceropegia (small flies), Hoya (Fig. 1798) (bees), Araujia (humble bees) 

 and Gomphocarpus (hive bees). 



Fig. 1798. — Hoya carnosa. Flower in 

 face view. 



Oleaceae 



The members of the Oleaceae are mostly trees or shrubs which are 

 widely distributed both in temperate and tropical regions. Many are 

 cultivated in Britain, and some, though not native, have become so familiar 

 that they form an accepted part of our flora. 



Among the truly British members we may mention first the Ash 

 {Fraxinus excelsior). Ligustrum vidgare (Privet) also occurs wild, though it is 

 best known as an evergreen garden shrub which is extremely accommoda- 

 ting, in that it will grow almost anywhere, and will withstand cutting almost 

 indefinitely. The golden privet, a form in which the leaves are yellow- 

 orange, is frequently planted as an ornamental shrub. Among other 

 commonly planted genera are Syringa (Lilac), Forsvthia, Jasmimim (Jas- 

 mine) and Olea (Olive). 



The plants are woody with opposite, decussate, simple or compound 

 jeaves and are sometimes evergreen. Several buds are often developed 



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