122 THE FLOWERING PLANT. 



field-mice, which, if left to themselves, would cause the extinction 

 of humble-bees (here the pollinating insects) by demolishing 

 their nests. 



Some regular flowers, however, also court the visits of special 

 insects, and in these the nectar is excreted at the bottom of a 

 long corolla tube, and is only accessible to the long proboscis of a 

 butterfly or moth. 



An instructive comparison has been drawn between regular 

 and irregular flowers in reference to the number of insect visitors. 

 The following conspicuous regular flowers, with nectar easily 

 reached, have the number of useful guests shown by the figures : — 

 Meadow buttercup (over 60), blackberry (67), wild strawberry 

 (25), hawthorn (57). In striking contrast to this are larkspur 

 and monkshood (larger bees only), foxglove (3), toad-flax (about 

 9 bees), early purple orchis (8). All these are conspicuous, 

 irregular, and with nectar difficult to reach. 



Honey-Guides. — Many flowers are spotted or streaked with 

 bright colours in such a way as to indicate the position of the 

 nectar. The petals of geraniums and the lower lips of many 

 labiate corollas show this. Prickles may also serve as " path- 

 pointers." When intended to keep off creeping insects, they are 

 generally directed downwards, while, if turned up, they may have 

 the other function. Both these points are illustrated by the 

 involucres of thistles. 



Honey or Nectar. — As already shown, this may be excreted by the 

 most various parts. It is always situated deep down in the flower. 



Pollen. — This, as stated above, is either rough or sticky, being 

 thus adapted for clinging to the bodies of insects, and at the 

 same time prevented from being blown away. Where the 

 arrangements for effecting crossing are simple, many stamens 

 and much pollen may be present, while if these are complex the 

 converse is often true. 



We will now take a few special cases in illustration of the 

 points involved in cross-pollination, commencing with simple 

 regular flowers, and ending with complex irregular ones. Space 

 will only admit of very brief descriptions. 



I. Regular Flowers. — Buttercups are as simple here as in 

 structure. Numerous small insects are attracted by the yellow 

 colour, and in obtaining the nectar, are pretty sure to get dusted 

 with pollen, especially as the outer stamens are matured first. 

 Moderately proteranclrous. 



The poppy is visited for pollen, of which a superabundance is 

 formed by the numerous stamens. The broad flattened top of 

 the pistil is well adapted as an alighting platform, and it also 

 bears the radiating sessile stigmas. 



