242 FLOWERS AND THEIR WORK. 



reduced to hair-like structures, those above the stamens being longer, 

 directed downwards, and lying in the contracted portion of the spathe. 



If the flower under examination has recently opened, we find that 

 the female flowers only are mature, but if it is one that has been 

 open for some time, the female flowers are beginning to develop 

 into fruits, and at the same time secrete a sweet fluid, while the male 

 flowers are shedding their pollen. Thus the female flowers are not 

 pollinated by the agency of the male flowers above them ; how then 

 are they pollinated ? 



On opening the lower part of the spathe we always find within 

 it a number of little flies ("midges") which have been assisted in 

 finding their present abode by the conspicuous nature of the spathe 

 and spadix. All these flies are more or less dusted with pollen col- 

 lected either here or from flowers previously visited. When the flies 

 visit an Arum during its first or female stage, they find no food, and 

 crawl about in their attempts to escape ; but they are securely 

 entrapped by the hairs at the neck of the spathe, which hairs, pointing 

 downwards, allow easy access to the interior, but effectually prevent 

 escape. However, in their movements the flies rub their bodies over 

 the sticky stigmas, placing on them pollen previously obtained in 

 other Arums. 



The fertilised ovaries now begin to develop into fruits, while the 

 anthers open, shedding their pollen over the bodies of the imprisoned 

 flies. Then the hairs wither, setting free the flies after the work of 

 pollination has been effected, and after they have become covered with 

 pollen to prepare them for a repetition of the process in other Arums. 



267. Flowers with partially Concealed Honey. Many 

 flowers have arrangements for concealing the honey from the 

 shortest-tongued insects, so that the visiting insects must 

 have tongues at least about 4 mm. in length to reach it. 

 The honey may be slightly concealed by the stamens e.g. 

 Buttercup, Stitchwort ; by the erect, stiff sepals in the 

 smaller Crucifers ; by the formation of a shallow receptacle- 

 cup in many E-osaceae e.g. Strawberry, Cinquefoil; or by 

 a short corolla-tube e.g. the shorter- tubed Composites and 

 Labiates, Valerians, Yiburnum, G-uelder Rose, Speedwell. 

 Such flowers are visited by the longer-tongued beetles and 

 flies, as well as by insects of higher type. 



268. Flowers with fully Concealed Honey. This type 

 of flower differs only in degree from the last. Here the 

 honey is out of the reach of the short-tongued insects, and 

 can only be obtained by those having tongues about 6 mm. 

 long, including the longest-tongued flies (chiefly the Hover- 



