THE AMERICAN BOTANIST 



89 



In passing on to consider the brown algae it may be sug- 

 gested that the laboratory study of but two types is sufficient 

 for such an isolated group. As mentioned above, Ectocarpus 

 and Ciitleria are preferable to Fucus, inasmuch as in the first, 

 we have simple filamentous body-structure passing into thalloid, 

 and in the second thalloid, purely with very instructive differ- 

 entiation of gametes ; while the third type involves at once the 

 complex thallus structure along with fully differentiated repro- 

 ductive organs. 



The red algae may conveniently be treated by examination 

 of the usual laboratory types, NemaUoji and Polysiphonia. 

 Perhaps one need not be too chary of finding homologies with 

 the Coleochaetaceae, and of instancing the parasitic species in 

 preparation for later study of the Ascom3^cetes. It ma}^ be well 

 to remind authors here that the institution of the sporophyte 

 generation is something that took place in time ; that the reduc- 

 tion divisions in the chromosomes that separate gametophyte 

 from sporophyte generations are simply an immediate occur- 

 ence in Coleochactc (and lower algae), a later incident of life- 

 history in the Rhodophyceae ; and that therefore the ''chasm" 

 between Chlorophyceae and Rhodophyceae is merely one of 

 arbitrary assumption. 



The Ascom3^cetes are best treated in immediate connection 

 with the red algae, for obvious reasons, and the homologies 

 deserve much more than the casual mention they usually receive. 

 An aquatic type should certainly be utilized to begin with, and 

 the lichenous form Collema is advisable as easily available. The 

 closest of homologies between this species and Rhodophycean 

 types may be traced, as regards the whole reproductive process 

 and organ-complex. The gradual ecologic shifts in habitat 

 (aquatic to terrestrial) and nutritive method (symbiotic to 

 parasitic) may be indicated for the group by following up 

 CoUeina Sphacrotlicca and with Pyronema. Only after con- 



