i INTRODUCTION 45 



capable of bending. They do not occur in stalks, or 

 non-geotropic roots such as those of the Ivy or Mistletoe, 

 while plants which develop starch grains nowhere else, 

 produce them in the root tips. Again, tbe flowers and 

 leaves of many plants which adopt special positions with 

 reference to the earth develop starch grains ; while 

 those of allied species, which assume no definite position 

 do not produce starch grains.' 



Conclusion 



One result which comes out with increasing clear- 

 ness from recent investigations is the great amount 

 of variability. In fact, it is becoming more and more 

 a surprise how the older botanists can have regarded 

 species as fixed and invariable. This is not only the 

 case in genera, such as Eubus and Hieracium, the 

 species of which have long been recognised as extremely 

 variable and difficult to define ; but it may almost be 

 said that, as a rule, when plants are studied under 

 dissimilar conditions, or in various parts of their area, 

 they will be found to present considerable differences, 

 so that, as our knowledge advances, the definition and 

 limits of species become, not more easy and definite, 

 as might perhaps have been expected, but more and 

 more difficult and debatable. 



Perhaps no part of Botany is more interesting 

 than the manner in which plants adapt themselves 

 to circumstances. The reasons suggested are in some 

 cases more or less hypothetical. Systematic and Mor- 

 phological botany may, no doubt, be treated with 

 scientific precision, by omitting all attempt at explana- 

 tion. Such works are often models of lucid description, 

 and afford a solid foundation on which to construct the 

 history of plant life. To many, indeed, systematic 

 botany is the most interesting department of the 

 science ; to others it is the entrance and outer court 



^ See, for a general discussion on the subject, F. Darwin, Bep. Brit. Assoc. 

 Cambridge (1905) ; also Nature, 1904. 



