THE FLOW Eli 119 



anthers are pressed against the end of tlie style. The 

 pollen grains are few and unusually small. Fertilization 

 is effected in the closed flowers, and abuudaut seed results, 

 the pods seeding far more freely indeed than those of the 

 oi'dinary flowers. In some species of Violet, tliese cleutog- 

 aiiious Howers are concealed under the leaves, or are borne 

 on runners underground. 



232. Self-fertilization prevented. — ilany flowers are 

 habitually fertilized either (1) by their own, or Ql) by 

 foreign pollen, — sometimes in one way, sometimes in tlie 

 other, as chance decides. In the great majorit}' of flower- 

 ing plants, however, cross-fertilization is the rule. Self- 

 fertilization may be absolutely prevented. This must be 

 the case when the flower Ijears only pistils (\h pintlUate^, 

 or stamens (is stam'uiate) . Sometimes the staiuinate and 

 pistillate flowers are produced on separate individual plants 

 (when the plants are said to be dioecioux ) ; sometimes on 

 the same plant (when tlie species is moHWcious). An 

 equally sure mode of preventing self-fertilization is seen 

 where the pistils and stamens, though both present, are 

 active at different times. This may well l:>e illustrated 

 by tlie common Plantain. The flowers are borne on long 

 spikes. Tlie unfolding of the flowers "proceeds from 

 base to apex of the spike in regular order, and rather 

 slowly. While the anthers are still in the unopened 

 corolla and on short filaments, the long and slender hairy 

 stigma projects from the tip and is receiving pollen blown 

 to it from neighboring plants or spikes : a day or two after- 

 wards, the corolla opens, the filaments greatly lengthen, 

 and the four anthers now pendent from them give their 

 light jJollen to the wind ; but tlie stigmas of that flower 

 and of all below it on that spike are withered or past 

 receiving pollen." ^ 



233. When the stamens mature first, as in many flowers, 

 the condition is termed proterandry . In the opposite ease, 

 ■proterogyny^ which is less usual, tlie pistils have been fertil- 

 ized or are no longer receptive by tlie time the antliers open. 



1 Asa Gray, " Structural Botany," p. 219, 



