chap, iv Taxonomy, 1 860-1 goo 119 



which had been developed in the Bryophyta. Both 

 vegetative and reproductive mechanisms had undergone 

 a fundamental modification which was inexplicable except 

 upon some such hypothesis. 



More active speculations were indulged in as to the origin 

 of the Pteridophy ta, but in the absence of evidence derived 

 from the preservation of fossil remains they remained 

 speculations only. Some morphologists, particularly 

 Campbell, suggested the origination of some such form 

 as Ophioglossum from a hepatic ancestor of the type of 

 Anthoceros. Bower, with perhaps more reason, sug- 

 gested the origin of the group from a primitive stro- 

 biloid form of which Phylloglossum may be the nearest 

 living ally. The original type he pictured as an un- 

 branched upright strobilus, in which all the leaves were 

 sporophylls, and the sporangia of moderate size. Such a 

 form he held might be traced back to a body of the 

 nature of a sporogonial head, development proceeding on 

 the lines of (i) sterilization of the potentially sporogenous 

 tissue ; (ii) formation of septa ; (hi) relegation of the 

 spore- producing cells to a superficial position ; (iv) eruption 

 of outgrowths (sporangiophores) on which the sporangia 

 are supported. 



Both Campbell and Bower agreed that in the series of 

 Pteridophyta the three existing classes have been developed 

 along parallel lines, having diverged separately from the 

 original ancestral type at early periods of their evolution — 

 an opinion that commanded general assent. 



The inter-relationships of the group gave rise to a great 

 deal of controversy, much of which centred round the 

 different families of the Ferns. Prior to 1890, largely 

 owing to the researches of Mettenius in 1864, it was con- 

 sidered that the Leptosporangiate forms were the more 

 primitive of these, and that they are consequently related 

 the most closely to the Algal or Bryophytic ancestors. 



