8 Proceedings of the Ohio State Academy of Scioice. 



Associated with the dominant species are others of minor 

 imjiortance, which however may he abundant and cons])icnous 

 enough in various jmrts of the association to lend character to 

 the vegetation of that part. Thus, in one part, Scirpus fiuviatihs 

 may be a dominating species of nearly equal rank with the Typha ; 

 we have then a Typha- Scirpus society in the Typha association. A 

 society may also consist of a single species only, as an isolated 

 tussock of Scirpus lacustris in a Typha association. The society 

 should always be clearly defined ; altho there is generally a 

 transition from one to the other at the margins. The societies 

 are designated by their principal species. With these are gen- 

 erally associated others of secondary importance, secondary 

 species, which may belong to the same or to another succeeding 

 or preceding association. In the latter case they show a relation- 

 ship to the society in which they occur. As for example, in a 

 Typha-Sphagnum society Potamogeton lonchites belonging to 

 an association of fixed aquatics, is frequently present, persisting 

 and growing well, even where the water has entirely receded 

 leaving a moist but not wet mud flat. The shoots of the 

 Potamogeton are shorter than those in the water but are green 

 and thrifty. That the plant does not suffer from the diminution 

 of water in the substratum seems to be due to the increased 

 humidity of the atmosphere at the level of the shoots.^*' Thus 

 the Potamogeton is benefited by the presence of the taller plants, 

 for if these were absent the Potamogeton w'ould soon succumb. 



The societies and associations may develop a zonal or an 

 alternate arrangement. The former term is used in this paper 

 to designate a more or less well defined crescentric arrangement 

 which results typically from a radial growth from a common 

 center. Alternation is used to designate scattered masses, ex- 

 hibiting no definite relationship in space to one another. The 

 location of each such mass is determined either by local condi- 

 tions or thru accidents of dissemination. 



Transects have been charted in a few areas to develop the 

 succession from one society or association to another. These 



