546 SUMMARY AND CHAP. XIL 



CHAPTER XII. 



SUMMARY AND CONCLUDING REMARKS. 



Nature of the circumnutating movement History of a germinating 

 seed The radicle first protrudes and ciicumnutates Its tip 

 highly sensitive Emergence of the hypocotyl or of the epicotyl 

 from the ground under the form of an arch Its circumnutation 

 and that of the cotyledons The seedling throws up a leaf-bearing 

 stem The circumnutation of all the parts or organs Modified 

 circummitation Epinasty and hyponasty Movements of climbing 

 plants Nyctitropic movements Movements excited by light and 

 gravitation Localised sensitiveness Resemblance between the 

 movements of plants and animals The tip of the radicle acts like 

 a brain. 



IT may be useful to the reader if we briefly sum up 

 the chief conclusions, which, as far as we can judge, 

 have been fairly well established by the observations 

 given in this volume. All the parts or organs in 

 every plant whilst they continue to grow, and some 

 parts which are provided with pulvini after they have 

 ceased to grow, are continually circumnutating. This 

 movement commences even before the young seedling 

 has broken through the ground. The nature of the 

 movement and its causes, as far as ascertained, have 

 been briefly described in the Introduction. Why 

 every part of a plant whilst it is growing, and in some 

 cases after growth has ceased, should have its cells 

 rendered more turgescent and its cell-walls more 

 extensile first on one side and then on another, thus 

 inducing circumnutation, is not known. It would 

 appear as if the changes in the cells required periods 

 of rest 



