138 Darwin on the Effects of Cross- and Self- Fertilization. 



I 0USi — how pollen, being a most nutritious substance, would 

 soon have been discovered and devoured by insects, and by 

 adticrinu- to their bodies be carried from anthers to stigma and 

 from one flower to another, — how a waste secretion, sucb as 

 honey-dew or glandular exudations, may have been developed 

 into nectar and utilized as a lure, — the interesting illustrations 

 of the vast amount of pollen pre- lilous plants, 



and the great distances to which their light pollen is often 

 carried by the wind, — all these inviting topics we must now 



In passing we note the remark that il the excretion of a sweet 

 liquid by glands seated outside of a flower is rarely utilized as 

 a means of cross-fertilization by the aid of insects ;" and the 

 sole exception alluded to is that of the bracts of Mar< 

 But a parallel case is afforded by many species of h 

 and notably in a strii i in conservatories, 



under the name of Poinsettia. Here the attraction to the eye is 

 supplied by the intense red coloration of ordinary leaves placed 

 next to the inflorescence, and that to the palate or tongue (it 

 either term may be allowed), by a large cup-shaped gland on 

 the side of the involucre, which contains or surrounds the 

 naked and greatly simplified flowers of both sexes._ 



That anemopnilotis plants arc prevailingly diclii 

 monoecious or dioecious) is speculatively connected with their 

 antiquity; that they are very largely trees or shrubs is because 

 " the long life of a tree or bush permits of the separation of the 

 sexes with much less risk of evil 



failing, and seeds not being produced, than in the case of short- 

 lived plants. Hence it probably is, as Lecoq has remarked, 

 that annual plants are rarely dioecious." The number of 

 anemophilous species is comparatively small, but that of indi- 

 viduals of the species strikingly large, so that they form of 

 themselves, in cold -, where plant-ir"''" 



ing insects are fewer, ei: of Coniferae, bi 



beeches, etc., or meadows, and glades, as of grasses, sedge 

 rushes. Being thus either necessarily or prevailingly 



: . and luv^arious, it is nor u- 1 



hold their own unchanged in various parts of the world. Still 

 their advantage is gained at the expense of the production of 

 an enormous superfluity of pollen, a costly product ; and, when 

 dioecious, half the individuals produce no seed. Hermaphro- 

 ditism with dichogamy, or some equivalent, and transportation 

 by an appeal to the senses and appetites of insects, secures all 

 the advantages with least expenditure. The earliest 

 tion in plants took place by tl t 1 i < n of the feitilizing or 

 even of the : . in manner of most of the Algae: 



mainly losing this as vegetation became terrestrial, the transpor- 



