TABLE OF CONTENTS 



I. The Special Senses of Plants, J. C. Arthur 1 



Eighteenth centtiry opinions — Application of terms — 

 Knowledge of mechanism — Primary unity with great di- 

 versity — What constitute special senses — Sense of con- 

 tact — Trend of sense development — Free and fixed organ- 

 isms — Discovery of gravity sense — Movement connected 

 with growth — Transmission of impulses — Sensitiveness 

 to light — Chemical sense — Moisture sense, 



II. The Development of Irritability, D. T. Mac- 



DOUGAL 19 



Derivation of existing forms — Chlorophyll and sunlight — 

 Pollination — Organization of shoot — Distribution of nu- 

 tritive factors — Sensory and motor zones — Development 

 of root functions — Nutritive factors in soil— Organization 

 of roots. 



III. Wild Lettuce as Weed and Compass Plant, J. 



C. Arthur 31 



Likeness to cultivated lettuce — General characters and 

 habit — First appearancein America— Fifteen years of con- 

 quest — Seeds and their distribution — How to be a success- 

 ful weed — Even a weed may be interesting — The habit of 

 polarity — Another compass plant — Explanation of the 

 peculiar trait. 



