CHANDLER FULTON 



291 



like a Cordyloplwra colony in that 1 ) there is more branching than 

 in an actual colony, and 2) the uprights are too tall relative to 

 their parent stolons. 



The geometric progression model was redrawn in terms of the 

 appearance of colonies growing under standard conditions, as 

 shown in Figure 2. The growth during any unit of time is indicated 

 by a pattern: black, stippled, etc. The stolon is visualized as grow- 



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Time units 



Figure 2. A model illustrating the growth of a hypothetical colony over 

 a period of six time units. See text for explanation. 



ing one unit per unit time (i.e., linearly), and producing uprights 

 at a rate of one per unit time. During the same time unit, an upright 

 grows only one-half unit, and a side branch only one-quarter unit. 

 However, uprights and side branches continue to produce new 

 tubes at the same distances as uprights are produced by stolons 

 (i.e., one unit), and thus produce new' tubes at rates of 0.5 and 0.25 

 tubes per unit time respectively. 



Such a model takes into account the linear growth of tubes and 

 normal branching pattern, and gives rise to a two-dimensional 

 colony which bears a striking resemblance to laboratory colonies 

 (cf. Figs. 1 and 2), If one computes the increase in hydranth num- 

 ber of such a hypothetical colony with time, however, one finds that 

 it continually falls away from exponential. This is in contrast to act- 



