200 THE STEUCTUllE OF FLOWERS. 



the habit of blossoming early, as in the spring or the begin- 

 ning of the summer, are protogynous ; such are species of 

 Hellebore, Frunus, and Gratcegus, as well as the Horse-chestnut 

 and Mandragora vernalis. 



Some species are characterized by the habit of living in 

 shady places, as Geum urhanum and G. rivale, Chrysospleiiium 

 oppositifolium, Gagea lutea, Paris quadrifolia. 



Lastly, others have minute flowers, as Geranium pusillum, 

 Veronica serpyllifolia, Tojjieldia, and many other species, some 

 of which I have mentioned when treating of the emergence 

 and development of the floral whorls, where I have explained 

 the cause. * 



Wind- fertilised or anemophilous flowers are for the most 

 part protogynous ; for these flowers have been accompanied by 

 strong degeneracy of the coi'olla and pollen, while all traces 

 of nectariferous structures are almost invariably and entirely 

 suppressed.! Hence Thalictrum minus, Polerinm. Sanguisoyba, 

 Plantago sp., Callitriche, Myriophyllum, Artemisia, Cheno- 

 podium, Amentiferce, Juncacece, and Graminece are all more 

 or less characterized by being protogynous while they are 

 anemophilous as well. 



If we are not in a position to trace the actual causes of 

 protogyny in every instance, we can at least see several 

 influences which can bring it about. Temperature will be 

 seen hereafter to be a most potent one ; for a relatively lower 

 temperature very frequently checks the energy of the corolla 

 and stamens, without having any necessarily corresponding 

 effect on the pistil, and several compensating processes then 

 come into play; so, conversely, the pistil now gains the 

 ascendancy and can mature first. This, therefore, will 



* See Chaps. XX. and XXI, 



t Intercrossing by insects may be recovered in anemophilous flowers ; 

 when honey may be again secreted, as in Salix caprcea and Sanguisorba 

 officinalis ; see Fertilisation, etc., p. 236, fig. 77. 



