192 SIZE A FACTOR IN STELAR MORPHOLOGY [CH. 



of Similar Structures as applied to the vascular system of Ferns may react 

 finally upon their phyletic seriation. But none the less, when once this 

 reservation has been made, the characters of the vascular system remain as 

 the most important structural features for the phyletic treatment of the 

 Class. Subject to certain limitations, the degree of disintegration of the 

 stele, or of the leaf-trace, may still be held as giving a trustworthy indication 

 of the degree of phyletic advance of the Fern that shows it. 



Postscript to the Chapters on Vascular Anatomy 

 The attempt thus to place the comparative study of the vascular system 

 of the Filicales upon a physiological-anatomical-phyletic footing is plainly 

 out of harmony with other views which have been advanced upon grounds 

 of purely anatomical comparison. It has already been stated that anatomy 

 cannot stand alone as a branch of enquiry, but must be coordinated and 

 harmonised with other lines of comparative study. Least of all is the anatomy 

 of the adult structure in the mature state sufficient. The adult should always 

 be interpreted in the light of the ontogeny. It must also be stated that to 

 anticipate for the results of anatomical enquiry a logical sequence is wholly 

 to misunderstand its place in Biological Science. Evolution has followed 

 lines of opportunism, not of logic. In its study this should be constantly 

 borne in mind. 



No attempt has been made in the foregoing Chapters to argue out the 

 differences of opinion which have arisen, especially those relating to the 

 origin of the pith. All that has been done has been to state the case as it 

 appears to follow from observations of the ontogeny as well as of the adult 

 structure, in a number of examples specially selected as being themselves 

 relatively primitive : this method should be checked by comparison based 

 on a study of other criteria than that of structure alone, as well as by 

 reference to geological sequence. But in order to assist readers desirous of 

 forming an independent opinion on the validity of the views here put for- 

 ward, and of comparing them with the views of other authors, a list of 

 Literature bearing on the question of the stelar morphology in Ferns is 

 appended, and it has been made as comprehensive as possible. 



BIBLIOGRAPHY FOR CHAPTERS VII, VIII, AND X 



119. De Bary. Comparative Anatomy. Engl. Edn. Oxford. 1884. 



120. Van Tieghem. Sur la Polystelie. Ann. Sci. Nat. Bot. Ser. 7. 1886. 



121. Le Clerc du Sablon. Ann. -Sci. Nat. Bot. Ser. 7. Vol. ii, p. i. 1890. 



122. POIRAULT. Rech. sur les Crypt. Vase. Ann. Sci. Nat. Bot. S6r. 7. Vol. xviii, 

 p. 113. 



123. Harvey Gibson. Sclagiiielln. 1894. Ann. of Bot. viii, p. 171. 



124. Zenetti. Osmunda. Bot. Zeit. 1895, p. 75. 



125. Cormack. Polystelie roots of certain Palms. Trans. Linn. Soc. Vol. v, 1896, p. 275. 



