FIRST LECTURE. 



THE EVOLUTION OF THE SPOROPHYTE IN THE 

 HIGHER PLANTS. 



DOUGLAS HOUGHTON CAMPBELL. 



THE questions relating to the origin of organic structures 

 must always possess great interest for the biologist, and when I 

 was asked to speak before the students at Woods Holl, it 

 seemed to me that a discussion of recent views bearing on the 

 development of the spore-producing structures of the higher 

 plants, i.e., the Archegoniates and seed-bearing plants, would 

 not be inappropriate. 



There is good reason to suppose that among plants, as among 

 animals, the most primitive forms were aquatic ; and it is highly 

 probable that many existing fresh-water algae are but slightly 

 modified descendants of these ancestral types. This is evinced 

 by the great uniformity shown by existing green algae all over 

 the world. Most genera and many species are cosmopolitan, 

 and they exhibit far less variety than is shown by their larger 

 and more specialized marine relations. Presumably the condi- 

 tions in fresh water have changed but little, and as the more 

 specialized forms have taken to the land, or have developed in 

 the sea, the few that remained in their primitive environment 

 have been subjected to much less competition, and have prob- 

 ably persisted with but little change from very remote times. 



Leaving aside certain forms of doubtful affinities, like the 

 bacteria and blue-green algae, the existing forms which repre- 

 sent most nearly the ancestors of the higher plants are the 

 Volvocineae and Protococcaceae. The former are, as all bota- 

 nists know, free-swimming green organisms which show resem- 



