XXXVl INTRODUCTION. 



use of students in most departments of biology. It 

 will suffice to allude, in support of these statements, 

 to the writings of Mr. Darwin on such subjects 

 as rudimentary organs, the use or disuse of certain 

 parts according to circumstances, the frequently ob- 

 served tendency of some flowers to become structurally 

 unisexual, the hability of other flowers perfectly 

 organised to become functionally imperfect, at least 

 so far as any reciprocal action of the organs of the 

 same flower is concerned, reversions, classification, 

 general morphology, and other subjects handled at 

 once with such comprehensive breadth and minute 

 accuracy of detail by our great physiologist. 



In the follomng pages alterations of function, unless 

 attended by corresponding alterations of form, are 

 either only incidentally alluded to, or are wholly passed 

 over ; such, for instance, as alterations in the period 

 of flowering, in the duration of the several organs, and 

 so forth. ^ Pathological changes, lesions caused by 

 insect puncture or other causes, also find no place in 

 this book, unless the changes are of such a character 

 as to admit of definite comparison with normal con- 

 formation. Usually such changes are entirely hetero- 

 niorphous, and, as it were, foreign to the natural 

 organisation. 



The practical applications of teratology deserve 

 the attention of those cultivators who are concerned 

 in the embellishment of our gardens and the supply 



' A curious illustration of the latter class of alterations came under 

 the writer's notice last summer (1868), and which he has reason to 

 believe has not been previously recorded, viz. the persistence in an 

 unwithered state of the petals at the base of the ripe fruit, in a straw- 

 beiTy. All the fruits on the particular plants alluded to were thus 

 provided as it were with a white frill. Whether this be a constant 

 occurrence in the particular variety is not known. 



