200 THE STRUCTURE OF FLOWERS. 



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

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

 Hellebore, Prunus, and Crataegus, 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, GhrysospleniuTYi 

 oppositifolium, Gagea lutea, Paris quadrifolia. 



Lastly, others have minute flowers, as Geranium piisilluvi, 

 Veronica serpyllifolia, Tojfieldia, and many other species, some 

 of which I have mentioned Avhen treating of the emergence 

 and development of the floral whorls, where I have explained 

 the cause. * 



Wind-fertilised or aneraophilous flowers are for the most 

 part protogynous ; for these flowers have been accompanied by 

 strong degeneracy of the corolla and pollen, while all traces 

 of nectariferous structures are almost invariably and entirely 

 suppressed.! Hence Thalictrum minus, Poterium, Sanguisorha, 

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

 podium, AmentifercB, Jimcacece, and Graminece are all more 

 or less characterized by being protogj^nous 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 energj^ 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 caproea and Sanguisorha 

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



