582 THE FERTILISATION OF FLOWERS. [PART Iv. 
Although, from the peculiar industry of bees, elongation of the 
corolla-tube is to be ascribed to their influence in the great 
majority of cases, this is not the case always. The flowers of 
Scrophularia and Symphoricarpus are just of the right size to admit 
a wasp’s head ; and wasps are attracted in such numbers to these 
flowers by the abundant honey that the visits of other insects to 
which the honey is equally accessible are greatly diminished. 
Other flowers conceal their honey in tubes so long and narrow 
that it is only accessible to Lepidoptera. Owing to the small 
supply of food needed by Lepidoptera and their inferior industry, 
such a condition could only prove advantageous to a comparatively 
small number of plants. The following native flowers are adapted 
for Lepidoptera :—DiuRNAL FLOWERS: Anacamptis pyramidalis, 
species of Dianthus, Lychnis Githago; NocruRNAL FLOWERS: 
Gymnadenia conopsea, species of Platanthera, Saponaria officinalis, 
Lychnis vespertina, Lonicera Caprifolium and L. Perielymenum. 
Of these, the diurnal flowers exclude bees (and still more, other 
insects) by the narrowness of their tubes, and the nocturnal species 
by their length also. 
In many flowers the mouth of the corolla closes, and can be 
forced open by bees but not by flies; the visits of the former are 
therefore increased and of the latter diminished. I may merely 
refer to the closed mouth of the corolla in Antirrhinum and 
Linaria, to the closed entrance to the nectary in Borago, Symphytum 
and Salvia, and to the close-shut flowers of Lathyrus pratensis, 
Vicia sepium, Pisum sativum, and many other Papilionaceze. In 
many cases such conditions fail to exclude the thin tongues of 
Lepidoptera. 
Effect of Concealment of the Pollen. 
Freely exposed pollen is liable to be spoilt by rain, devoured by 
flies and beetles, or carried away by pollen-collecting bees. Of 
these contingencies the first is wholly an evil, the second becomes 
advantageous if any considerable amount of pollen is conveyed to 
the stigma, and the third almost always results in fertilisation and 
is therefore altogether advantageous. Concealment of the pollen, 
as of the honey, must have been brought about in the first place as 
a protection from rain. Since with this advantage comes the 
disadvantage that the sheltered pollen is less likely to be touched 
and placed on the stigma by insect-visitors, concealment of the. 
stamens has not become general. Many, even of those flowers 
whose honey is deeply placed and attainable by a limited group 
