SPRING FLOWERS 133 



Owing to the length of the corolla tube, only long-tongued insects 

 can reach the nectar, and the visitors observed are long-tongued 

 flies and occasionally humble-bees. When an insect visits a short- 

 styled flower its head will be dusted with pollen. Should it now 

 pass to a long-styled flower this pollen will be deposited on the 

 stigma. At the same time, pollen will be deposited from the 

 stamens of this form about half-way up the proboscis of the insect. 

 When the latter visits a short-styled flower this region of the tongue 

 will touch the stigma, which will thus receive pollen from stamens 

 of the corresponding height. 



The ovary of a flower that has been fertilised enlarges and 

 develops into the fruit, which is surrounded by the calyx, while 

 the corolla disappears The fruit contains a number of seeds, and 

 opens, by splitting at the summit into ten short teeth. These roll 

 back so that the seeds, as they become detached from the pro- 

 jection from the base of the seed - capsule, can fall out of the 

 fruit. 



THE LESSER PERIWINKLE (Vinca minor, L.). 



Two kinds of Periwinkle can be found wild throughout Britain, 

 growing usually in the shade of trees in open woods or on hedge- 

 banks. The Greater Periwinkle (Vinca major) is less common, 

 but is commonly grown in gardens. The Lesser Periwinkle is 

 well established in many places, and often covers the soil of open 

 woods to the exclusion of most other plants. Neither of the 

 species is probably a true native of this country, and there is 

 reason to believe that the introduction of both the larger and 

 smaller kind took place at the time of the Roman occupation 

 of Britain. The plants flower in April and May, though occa- 

 sional flowers can be met with in the autumn. Either will serve 

 for study, the description being based on the commoner Lesser 

 Periwinkle (Fig. 67). 



This is a small perennial plant with dark green, glossy, 

 evergreen leaves. It spreads largely by vegetative growth. At 

 the level of the soil prostrate creeping shoots will be found. From 

 some of the nodes of these shoots, which persist for years and 

 become tough and woody, the buds grow up as more slender 



