514 



BOTANY 



etc., are familiar examples of these extremely efficacious adaptations. 

 While these appendages usually belong properly to the fruit itself, 



sometimes, as in the Bur- 

 dock (Lappa), the hooks 

 are appendages of the invo- 

 lucral leaves surrounding 

 the head of fruits. 



The Compositse, the 

 largest family of the Sper- 

 matophytes, offers an espe- 

 cially great variety of these devices for 

 distributing the seeds, the efficiency of 

 which is attested by the extraordinary 

 success these plants have shown for 

 holding their own in the struggle for 

 existence. 



POLLINATION 



Many of the most remarkable modifica- 

 tions of plants are connected with the 

 pollination of flowers. In the lower types 

 of Spermatophytes, especially the Gym- 

 nosperms, the conveyance of the pollen 

 to the ovule is largely the result of 

 chance, and depends upon the wind. 

 Wind-pollination is also known as "Ane- 

 mophily." Still, as the pollen and ovules 

 are produced in different flowers, cross- 

 fertilization is effected. In the lower 

 Angiosperms, like the various Arnentaceae, 

 i.e. Oaks, Poplars, etc., wind-pollination 

 is the rule, and, in these forms, diclinous 

 flowers prevail, so that self-pollination is 

 precluded. Other characteristic groups 

 of wind-pollinated plants are 

 the Palms, Grasses, and Sedges. 

 In all such forms the amount 

 of pollen is very large and the 

 pollen-grains are smooth and 

 small, so that they are readily 

 carried by the wind. The 

 stigma is frequently long and 

 feathery, so that it readily 

 catches the pollen-spores which fall upon it. 



In most of the anemophilous trees of northern regions, the flowers 





Fia. 480. Rhizophora mangle. Fruit 

 germinating before it falls; a, the point 

 where the enlarged hypocotyl becomes 

 detached. (After BAILEY.) 



