342 ORGANOGRAPHIC COMPARISONS [ch. 



It is possible to derive all types of their prothalli from the simple filament, 

 and many of them show this structure in their first development from the 

 spore, while a few retain it permanently. The antheridia and archegonia 

 have also been compared one with another, and partly from this, partly from 

 the suggestive intermediate states seen between antheridia and archegonia 

 in certain Bryophytes, it appears probable that these apparently distinct 

 organs were differentiated from a single type of gametangium, which was 

 terminal on branches of a filamentous thallus. These features, together with 

 the opening of the gametangia in water, and the motility in water of the 

 spermatozoids, suggest a reference to an Algal origin. But the gametophyte 

 generation of Ferns is not yet referable to any definite type of known Algae. 



The embryology of Ferns did not appear to yield any intelligible sug- 

 gestions of phyletic value so long as the types of embryo with a suspensor 

 were unknown. But now that a suspensor has been found in a number of 

 relatively primitive Ferns, it would appear probable that this organ is an 

 archaic feature, and that it was shared by early Filicales with the Lycopo- 

 diales. It is, however, apt to be eliminated in the more advanced types. This 

 seems to be a natural conclusion from the known facts. Professor Lang has 

 extended the comparison on the one hand to the Seed-Plants, in which also 

 a suspensor is the rule, and on the other to the Bryophytes (310, 311). Many 

 of these suggest by the first segmentations of their sporogonia a derivation 

 from the filamentous construction. The basal cell of the sporogonium of the 

 Jungermanniaceae is specially significant. Such a widespread reference of 

 the young sporophyte to a filamentous origin as is indicated by the first 

 steps of the ontogeny cannot be overlooked. Especially does it claim attention 

 where, as not uncommonly happens, the filamentous suspensor makes an 

 awkward curve of the embryo necessary before the shoot can take the usual 

 upright position. The facts appear to point to a filamentous construction 

 underlying the first steps of the ontogeny of the sporophyte in large sections 

 of the plant-kingdom, a feature which certain of the most primitive of the 

 Filicales share(3ii). Thus in both generations of Ferns, the facts suggest 

 a reference of the initial structure back to a filamentous source, such as is 

 seen in the general development of the soma not of any special types of 

 Algae alone, but of Algae in general. Moreover this comparison receives 

 further support in that certain Algal types show a filamentous stage preceding 

 a more massive development, but still of the same "generation." For instance 

 the Ckantransia filaments lead to the more complex Lemanea stage: or 

 the filamentous proembryo leads to the more complex segmented shoot of 

 Chara. It would be an error to drive such comparisons into detail in the 

 present state of our knowledge. All that is suggested here is that a precedent 

 filamentous stage, leading to a more complex somatic development, is seen 

 in both the generations of the Filicales: and that a like progression can be 



