CONTENTS ix 



CHAPTER PAGE 



(IV) i. Commensalism and saprophytism 752 



2. Parasitism 761 



Fungi and bacteria 762 



Seed plants 769 



Grafting 776 



Galls 780 



Autoparasitism ......... 786 



3. Reciprocal parasitism, helotism, and endosaprophytism . . 786 



Root tubercles and their bacteria ...... 787 



Mycosymbiosis . . . . . . . . . .791 



Lichens 800 



Green-celled animals 803 



V. Reproduction and dispersal 805 



1. Reproductive behavior in seedless plants ..... 805 



Vegetative reproduction ........ 805 



Asexual reproduction ........ 809 



Sexual reproduction 816 



2. Flowers 825 



Role 829 



Wind pollination ......... 834 



Water pollination 838 



Insect pollination ......... 838 



Geitonogamy .......... 862 



Autogamy .......... 863 



Protective features 869 



Origin of floral structures 875 



3. Influence of external factors upon reproductive organs . . 878 



Seedless plants 878 



Origin of sexuality 881 



Artificial. parthenogenesis ....... 882 



Sexuality in the fungi ........ 883 



Bryophytes and pteridophytes 884 



Seed plants 885 



Vegetative and reproductive periods 885 



Sex determination ........ 895 



Flower color 898 



Size and number of floral organs ...... 900 



Flower form .......... 900 



Hybridization .......... 904 



Bud variation 904 



4. Fruits and seeds 904 



Protective structures 906 



Food accumulation . . . . . . . . .911 



Variation in relation to external factors . . . . .916 



Dehiscence . . . . . . . . . . 919 



Dispersal 919 



Origin of seed structures 928 



Planting of seeds 928 



VI. Germination 930 



Vivipary ...,,.... . 930 



