XX11 CONTENTS. 



lenation of the skunk's cabbage, 655. Spiders have discov- 

 ered this curious relation of the flowers and insects, 657. 

 Pollenation of jack-in-the-pulpit, 658. Pollenation of or- 

 chids, 660. Pollenation of canna, 664 page 351 



CHAPTER LI. 



SEED DISTRIBUTION. 



Means for dissemination of seed, 672. The prickly lettuce, 676. 

 The wild lettuce, 677. The milk-weed or silk-weed, 678. 

 The virgin's bower, 680 page 368 



CHAPTER LII. 



STRUGGLE FOR OCCUPATION OF LAND. 



Retention of made soil, 681. Vegetation of sand dunes, 683. 



Reforestation of lands, 684. Beauty of old fields, 689. .page 374 



CHAPTER LIII. 



SOIL FORMATION IN ROCKY REGIONS AND IN MOORS. 



Lichens, 690. Lichens are among the pioneers in soil forma- 

 tion, 691. Other plants of rocky regions, 692. Filling of 

 ponds by plants, 694. A plant atoll, 695. Topography of 

 the atoll moor, 696. A floating inner zone, 698. How was 

 the atoll formed? 700. A black-spruce moor, 703. Fall of 

 the trees of the marginal zone when the windbreak was 

 removed, 704. Dying of the spruce of the central area, 705. 

 Other mbrainic moors, 708. The bald cypress (taxodium), 

 711 page 381 



CHAPTER LIV. 



ZONAL DISTRIBUTION OF PLANTS. 



On the margins of lakes and ponds, 712. On the banks of a 



stream, 716 page 400 



CHAPTER LV. 

 PLANT COMMUNITIES; SEASONAL CHANGES. 



Plants of widely different groups may exist in the same com- 

 munity, 720. Seasonal succession in plant communities, 



