88 THE AMERICAN BOTANIST 



branching filament. Aphanochaete (I admit a not very com- 

 mon genus) presents an ideal alga for the exemplification of 

 gamete-differentiation, together with the tendency toward con- 

 crescence of branches that eventually leads to the thalloid types. 

 The decided advantage of this genus in the presentation of 

 gamete-differentiation lies in the fact of its obvious and im- 

 mediate relationship with the preceding types and the succeed- 

 ing. Citations of Cutleria or Pandorina and Volvox are quite 

 beside the mark when such a satisfactory genus as Aphano- 

 chaete is available for the demonstration. Coleochactc soluta 

 serves as an excellent type for presenting the final differentia- 

 tion of the sex-cells and for the significant increase in size of 

 the fertilization-product, the sporocarp. C. scutata pictures the 

 transition of body-form from a concrescent filamentous struc- 

 ture to a leaf-like thallus. 



Right in this connection the problem of fungal origins is 

 to be best taken up — as far as the Phycomycetes are concerned ; 

 and it is well, pedagogically speaking, to utilize such vivid 

 transitional cases for the stimulus they offer to the student in 

 the direction of homologies and data of phylogenetic signifi- 

 cance. Bessey's consistent and courageous treatment of the 

 alga-like fungi in close (in fact immediate) relation with their 

 progenitors should have a more hearty assent, it seems to me, 

 than we have given it. And there is little difficulty in introduc- 

 ing the types through an ideal series. First the problem of 

 coenocytism is to be worked out in the algal ancestry ; and for 

 this Cladophora and Vauchcria serve excellently. In the latter, 

 the second problem, that of saprophytism, is raised and its 

 solution indicated in the occurrence of the "rhizoids". Sapro- 

 legnia next, with its incipient degeneration of the sexual 

 process, introduces the fungal types proper (the student might 

 well be referred here to the Phyllosiphonaceae). Albugo and 

 Rhicopus, illustrate the further adaptation to> aerial life and the 

 ultimate degeneration of gamete-differentiation. 



