276 E. A. ANDREWS. 



area of wax, though the latter presented many facets and edges. 

 To this evidence of discrimination in the surfaces settled on 

 should be added the fact that the tubes were not made on the 

 lowermost inches of strips of wood, even when there was no 

 plant present to shade the bottom (as above described) and few 

 tubes were attached to the more resinous parts of the wood, so 

 that the swimming Folliculina would seem to react to various 

 stimuli. 



Again in the experiments with strips of wood the tubes fastened 

 to the wood both in shallow and in deep water were noticeably 

 orientated with the mouth of the tube upward toward the surface 

 and the tubes were prevailingly situated lengthwise in the furrows 

 of the wood caused by the saw and grain. 



On the stems of Potamogeton also the tubes stand lengthwise 

 and generally with the mouths upward. On leaves the tubes 

 are generally more abundant upon the upper than the lower 

 surfaces and often are crowded toward the edges. 



The above response to light would lead to the successive coloni- 

 zation of upper leaves in the Elodea zone during the season and 

 would explain the common orientation of the tubes with mouth 

 upward. 



The responses to solids would lead to the rapid utilization of 

 most solids as basis for attachment of tubes. But evidently 

 some other factors must be concerned in the choice of certain 

 surfaces, or refusal of some, and in the selection of certain sites, 

 as grooves and especially the crowding into aggregates as if 

 aware of one another's existence. 



AGGREGATION. 



Though isolated cases or tubes of Folliculina are common on 

 leaves as well as upon material experimentally supplied in the 

 open and in the laboratory for the attachment of the swimming 

 forms, yet it is very noticeable that the great majority of Fol- 

 liculina tubes occur in groups as if arising as colonies from budding 

 or in some peculiar way associated with one another. 



While such aggregates are well shown in nature on leaves of 

 Potamogeton and Elodea they can be better illustrated from the 

 groups formed in aquaria on paper, glass and the surface film 

 of the water. 



