86 Morphology BOOK, i 



the range of floral structures within each group. Eichler 

 gathered together by way of preface to each order all the 

 most important works of different writers upon it, including 

 references to anatomical and histological detail, and 

 discussed the peculiarities of morphology from the stand- 

 point of the evolutionist. 



The view at first held of the nature of metamorphosis, 

 as we have already seen in another connexion, was gradually 

 modified as time went on. The view of the differentiation 

 of an original type under the influence of adaptation was 

 set out by Hanstein, and the actual metamorphosis of one 

 specialized organ into another was denied, to be re-asserted 

 however, by Goebel in 1880. In his paper in the Botanische 

 Zeitung of that date he concluded that sporophylls are 

 metamorphosed foliage leaves, for he observed that spor- 

 angia are met with sometimes on what appear to be 

 normal green leaves of Botrychium t and that where they 

 occur the vegetative development is reduced. Hence the 

 gradual change from the foliage condition by reduction to 

 the spore-bearing condition. 



In 1893 a theory radically opposed to that of Goebel was 

 put forward by Bower. Reference has already been made 

 to his elaborate researches on the spore-bearing members 

 of the whole group of the Pteridophyta. The first series 

 of these, which dealt with the Equisetinae and the Lyco- 

 podinae were then completed, and the relations of the 

 leaves to the sporangia in these groups were under con- 

 sideration. They led to the conception of the sporophyll 

 as originating from a sporangial or strobiloid form in which 

 the adequate development and distribution of sporangia 

 were the primary considerations. Hence Bower came to 

 the conclusion that the sporophyll occurred earlier than 

 the foliage leaf in such a strobiloid form, and therefore if 

 metamorphosis has played a part in the development at all, 

 its order has been from sporophyll to foliage leaf and not in 



