1G8 THE JOl'KN'AJ. OF BOTAN* 



distinct categories of algal construction. Both, in fact, represent a 

 device Eor the fertilization in situ of an oogonium more or less 

 immersed in the parental soma, instead of being freely exposed at 

 the surface. The agreement is in biological factors rather than in 

 structural details. What does emerge is the fact that such paral- 

 lelism of response, as expressed in the inception of spermatogamy, 

 must have been the consequence of the action of identical environ- 

 mental conditions ; and that, so far, the Lichen-fungus must trace 

 its origin to the same environment as that which has produced the 

 modern Floridean ; that is to say, to the formation of reef-pools in the 

 warmer seas. Farther interpretations will be bound up with the 

 story of the progression of the Florideae from the undoubted original 

 method of sexual reproduction in terms of flagellated gametes, now so 

 hopelessly lost, and difficult to trace. The complete history of the 

 Floridese is hence to be analysed by comparison with other existing 

 phyla of the sea which retain their flagellated phases, and the 

 secondary nature of their specialization has to be accounted for. In 

 doing this, one may hope to throw light upon the causes which simi- 

 larly induced the analogous mechanism of Lichen-fungi. 



That two such groups of Alga? as ' Brown ' and ' Red ' sea-weeds 

 should co-exist, apparently side by side in all the varied biological 

 stations of the sea, and yet be so remotely allied in somatic and 

 reproductive organization, is one of the most interesting botanical 

 problems of the sea. Since such wide divergence must be based on 

 some factor of fundamental significance in their respective vital 

 complexes, however, it may elude observation at first sight. Nothing 

 could more definitely illustrate the vast number of other marine 

 races with intermediate, older, or even more special characteristics, 

 that must have existed and disappeared, than such extreme diver- 

 gence of these two great residual phyla of modern seas, in which 

 Green Algae play but a minor part. Any light that can be thrown 

 on the organization of such old races, or may now be seen in the 

 fate of their much modified migrants of the land, should be welcome ; 

 and there can he little doubt that in Ascomycetes, Lichen-fungi, and 

 Laboulbeniacese, may be traced such suggestions of Pre-Floridean or 

 Para-Phaeophycean phyla. Without going into minute detail, the 

 differentiating characteristics of the existing types may be sum- 

 marized by saying that the Brown Alga; are highly organized 

 somatically, in virtue of a true parenchymatous mode of cell-con- 

 struction, and they still dominate the optimum stations of the sea, 

 with less insistent demands on their capacity to make good the 

 wastage of their reproductive cells, which hence remain in a com- 

 parativelv elementary grade of specialization. Red Sea-weeds, on 

 the other hand, are somatically of very inferior filamentous organiza- 

 tion, never truly parenchymatous, and presenting an entirely different 

 order of metabolism in their individual protoplasts, in virtue of which 

 they are relegated to more secondary positions in the biological 

 provinces of the sea. They become characteristic denizens of quieter 

 water and more shaded situations, as plant-forms of mediocre size, 

 but with wastage-problems intensified, and consequent extreme 

 specialization of their reproductive organization to the limit of 



