Ill] EARLY METHODS OF CLASSIFICATION 57 



detailed characters, using chiefly those of external form : but they also grouped 

 them by features of wider than generic application. For this purpose search 

 was made for differential data, and attention soon fell upon the annulus of 

 the sporangium. Bernhardi (1800) distinguished Filices Gyratae, and Filices 

 Agyratae. Swartz adopted this distinction, while the further difference was 

 recognised between Ferns with an oblique annulus {Helicogyratae) and those 

 with a vertical annulus {Cathetogyratae). Robert Brown {Prodromus^ 18 10), 

 who also adopted a classification according to the annulus, added the use 

 of venation, and founded the Families of Polypodiaceae, Gleicheniaceae, 

 Osmundaceae, and Ophioglossaceae. Kaulfuss added to these the Family of 

 the Marattiaceae. From this period the real establishment of the Natural 

 Families of the Class is dated by Bommer {I.e. p. 22). But the Polypodiaceae, 

 which bulked the largest in genera and species, monopolised to a high degree 

 the attention of the Pteridologists of the first half of the 19th century. On 

 the other hand, the general relation of the families was sometimes struck in 

 singular accord with modern views. For instance Mettenius(29) disposed them 

 thus: I. Polypodiaceae: II. Cyatheaceae: III. Hymenophyllaceae: IV. 

 Gleicheniaceae: V. Schizaeaceae: VI. Osmundaceae: VII. Marattiaceae: 

 VIII. Ophioglossaceae. It is difficult to understand why later writers should 

 ever have diverged from so reasonable a sequence as this. If its order were 

 inverted it would accord in essentials, though not in detail, with current views 

 as to affinity. 



The external characters of the vegetative system, and the venation of 

 the leaves: the "vestiture" by hairs and scales: the form and position of the 

 sorus: the presence or absence of an indusium, and its outline and position, 

 together with the details of the mature sporangium, were the chief characters 

 used by systematists up to the time of the Synopsis Filicum (1868). Of those 

 who followed that era the writer of all others who brought a new method and 

 fresh features into the classification of Ferns was Prantl. His views, already 

 put in practice in his monographs of the Hymenophyllaceae (1875) and 

 Schizaeaceae (1881), were summarised in the words "It is clear that the 

 System of the Ferns must express the results of anatomical and develop- 

 mental investigation (30)." But as he wisely adds, "the question is less clear 

 which state of organisation is the more primitive, and which the derivative," 

 Into these sentences are condensed much of the method and spirit of the 

 later systematic investigation of Ferns, — and indeed of plants at large. That 

 method applied in respect of the development of the sporangium by von 

 Goebel led him to distinguish and to designate the Leptosporangiate as 

 distinct from the Eusporangiate Ferns(35). He also proposed to use more fully 

 the features of the gametophyte for purposes of comparison. On the other 

 hand adult Fern-anatomy, already pursued by Mettenius, was placed upon 

 a fresh theoretical basis by Van Tieghem in his theory of the "stele," while 



