VI] SERIATION ACCORDING TO SEGMENTATION 115 



rangiate Ferns with their more regular and simple segmentation are typically 

 more delicate in the constitution of their vegetative organs, their leaves are 

 thinner, and their roots more slender. This accords with their longer-stalked 

 and smaller sporangia. The Osmundaceae take a middle position both in the 

 robustness of their vegetative organs, and in the size of their sporangia. 



It may seem to lie near to the hand to suggest that the character of the 

 apical region is determined by the bulk of the organ, and has no other signi- 

 ficance. That the relation between bulk and apical segmentation is not simple 

 and direct will be obvious enough to those who have any wide knowledge 

 of segmentation in Ferns. A comparison of sections of the lateral wings of 

 Fern-leaves drawn to the same scale sufficiently proves that the manner of 

 segmentation is not directly dependent on size. Trichomajies reiiifornie {B) 

 is the most massive of the four Ferns represented in Fig. 105, and it shows 

 a simple transverse segmentation: while Aspleniiini resecUun (C), which has 

 the more complicated alternate segmentation, is actually thinner at the 

 margin than (A) or (B). Again, the apical meristem of the large Tree Fern, 

 Amphicosmia Walkerae, with a stem several inches in diameter, shares its 

 regular three-sided segmentation with that of the stems of the most insig- 

 nificant of Leptosporangiate Ferns {Ann. of Bot. iii, PL XXI, Fig. 22). The 

 question cannot be summarily disposed of in this way. That there is some 

 relation between bulk and complexity of segmentation was pointed out thirty 

 years ago, and the facts brought forward in this Chapter sufficiently demon- 

 strate it for the main divisions of the Filicales. But it is not simple or direct 

 in the individual. It makes its appearance in the race. 



The differences of apical and sporangial segmentation in the Filicales 

 show such a degree of consistency that they cannot be interpreted in any 

 other way than as indicating an hereditary difference of constitution between 

 those more massive and those less massive. The distinction between Eu- 

 sporangiate and Leptosporangiate types is not merely based on the difference 

 of their sporangia, but on differences of all their parts, of which their sporangia 

 give a trustworthy indication. Such differences are apt to be retained by 

 them, notwithstanding that Leptosporangiates may become massive in certain 

 features, like the stems of Tree Ferns; or that Eusporangiates may become 

 more or less "filmy," as in the Todeas and filmy Danaeas. The more or less 

 massive type of constitution is thus an inherent and hereditary feature. 



The next question will be whether the one or the other end of the series, 

 thus indicated by constitution of all the parts, is to be held as the more 

 primitive. The earlier writers taking their stand on comparison rather than 

 on Palaeontological evidence, and seeing some superficial resemblance be- 

 tween the Hymenophyllaceae and the delicate structure of the Bryineae, 

 suggested an affinity between them. This was the view of Linnaeus, Sprengel, 

 Presl, and Bernhardi. Van den Bosch even went so far as to erect the 



