NECTARIES. 265 



To trace out the probable development of the 

 nectary is beyond our limits ; but, in a word, if it 

 be granted — and experiment is conclusive on the 

 point — that intercrossing does lead to greater vigour 

 in the resulting seed, then any variation making 

 intercrossing more certain will lead to a selection 

 favourable to the individual presenting that variation ; 

 so that transudation of sugary matters forming a 

 rudimentary nectary, and so attracting insects, will 

 tend to establish and extend the variation, by which 

 the flowers will become permanently nectariferous. 



The position of the nectaries in flowers, and the 

 organs of which they are modifications, differ with 

 the kinds of insects for which they are suited ; some 

 lie almost on the surface of the flower — e.g., in the 

 carrot, elder, ivy, &c. — but most are situated in its 

 deeper recesses, not only because this position draws 

 the visiting insect well into contact with the male 

 and female parts, but also because exposure to water, 

 in the form of rain or dew, injures the nectar, and 

 decreases its attractiveness. This fact is the counter- 

 part of the enormous length of proboscis possessed 

 by moths, butterflies, and bees. In many flowers, 

 strange devices save the sugary fluid, even in the 

 most persistent downpour — e.g., in the upstanding 

 white dead nettle, the upper lip is formed into -an 

 umbrella (see Fig. 66) ; in the Tropaeolum majus 

 (garden nasturtium), upright water-resisting hairs (see 

 Fig- 55) prevent rain travelling towards the spur ; and 

 in the useful Borago officinalis (borage), the drooping 

 habit of the flower, and the tube-like cavity formed 

 between the stamens, give perfect protection. 



