382 



HUTCHINSON'S POPULAR BOTANY 



FIG. 470. INDIAN CROCUS. 



Lip of flower showing fringes and 

 streaks of colour honey-guides. 



so strongly asserted that cross-fertilization pro- 

 duces a more vigorous and successful race. 

 What cross-fertilization by insect agency does 

 is to produce more brilliant individuals, and to 

 keep up large flowers of bright hue. In fact, it 

 produces a kind of floral aristocracy ; whilst the 

 principal work of the vegetable kingdom the 

 abstraction of carbon from the atmosphere, the 

 setting free of oxygen, the production of food 

 for the entire animal races is done mainly by 

 the less brilliant weeds and grasses and trees 

 the working classes." 



We have seen how certain bisexual flowers 

 adapt themselves to self-pollination ; we may 

 next consider how another class of flowers, also 

 bisexual, provide against it. This brings us to the phenomena of dichogamy, 

 upon which we must say a few words. The term is derived from the Greek 

 dicha, in two parts, and gamos, marriage ; and whenever the reproductive 

 organs (stamens and pistil) of a bisexual flower mature at different times we 

 have an instance of dichogamy, and the flower is said to be a dichogamous 

 flower. When the stamens mature first, so that the pollen in their anther- 

 lobes escapes before the stigma in the same flower is ready for pollination, 

 the flower is said to be protandrous (Greek proteros, before, and andros, 

 male) ; and this is the case in most species of Geranium,, Pelargonium, 

 Malva, Umbel liferse, Composite, and Campanulacese. When, on the other 

 hand, the stigma matures and loses its capacity for pollination before the 

 anthers of the same flower have shed their pollen, the flower is said to 

 be protugynous (Greek proteros, before, and gune, a female). Some species of 

 Magnolia., ArisLolochia, Scrophularia, and Plantago have protogynous flowers, 

 but they are much less common than are the other kind. 



The Meadow Cranesbill (Geranium pratense, fig. 460) the largest of our 

 British Cranesbills is a good example of a protandrous flower. It might 



at first sight be thought to be a 

 self-pollinating flower, for at the 

 time when the anthers dehisce 

 they are bent right over the 

 pistil; but at this stage in the 

 flowering the pistil is imma- 

 ture, and the stigmatic tissue 

 is protected from pollen falling 

 upon it. At a later period, how- 

 ever, when the anthers have di- 

 FIG. 471. INDIAN CROCUS. verged from the pistil, the latter 



Hairsof a portion of two of the fringes of the lip highly magnified. matures, its five branches 6X- 



