XXVlll INTRODUCTION. 



pilosis, in accordance with which certain parts assume a 

 different form from the rest, in order the better to fit 

 them for the performance of different offices. Should 

 growth and development be uniform and regular, that 

 is in accordance with what is habitual in any particular 

 species, there is no monstrosity, but if either growth 

 or development be in any way irregular, malformation 

 results. Hence, theoretically, the best way of grouping 

 cases of malformation would be according as they are 

 the consequences of : 1st. Arrest of Growth ; 2ndly. 

 Excessive Growth; 3rdly. Arrest of Development; 

 4thly, of Excessive or Irregular Development. 



In practice, however, there are so many objections 

 to this plan that it has not been found practicable to 

 carry it out. The inability arises to a great extent 

 from our ignorance of what should be attributed to 

 arrest of growth, what to excess of development, and 

 so on. Moreover, a student with a malformed plant 

 before him must necessarily ascertain in what way it is 

 malformed before he can understand how it became so, 

 and for this purpose any scheme that will enable him 

 readily to detect the kind of monstrosity he is examin- 

 ing, even though it be confessedly artificial and im- 

 perfect will be better than a more philosophical 

 arrangement which circumstances prevent him from 

 employing. 



The plan followed in this volume is a slight modi- 

 fication of that adopted by Moquin-Tandon, and with 

 several additions. In it the aim is to place before 

 the student certain salient and easily recognisable 

 points by reference to which the desired information 

 can readily be found. Under each subdivision will be 

 found general explanatory remarks, illustrative details, 

 and usually a summary of the more important facts 



