363 



The lake waters in October-December contain (Table XIII., 

 PI. XLVIII.) but a fraction — from a third to a tenth — of the 

 nitrogenous matter that is found in the channel. This is an 

 index of the relative poverty of Quiver Lake waters when 

 isolated as a separate unit of environment and dependent 

 upon creek and spring waters, mainly of seepage origin, for its 

 supply. This relative poverty, combined with the factors be- 

 fore discussed, lies at the basis of the relatively small plankton 

 production in this body of water in this year. 



1898. 



(Tables V., XIII.; PI. XXIX., XLIX.) 



There are 26 collections in this year at fortnightly inter- 

 vals, with an average of 2.44 cm. 3 as compared wi£h 2.13 in the 

 river, and a maximum of 42.14 on May 3 coincidently with the 

 vernal maximum in the channel (PI. XII.), which, however, 

 falls 6.46 cm. 3 , or 15 per cent., short of that in the lake. 



The parallelism in the movement of production noted to 

 a varying extent in prior years may be traced also in 1898. The 

 most striking coincidence is the agreement in the location and 

 relative development of the vernal pulse, and further resem- 

 blance may be seen in the June pulse and the December rise 

 in production. The small quantities of plankton in the lake at 

 other seasons and the fortnightly interval of collection render 

 the correspondences less obvious though perhaps not less sig- 

 nificant. 



During the low water of January and in the subsequent 

 flood (PI. XXIX.) there is little plankton in the lake (.02) as 

 compared with the river (.45 — see table between pp. 342 and 343), 

 though an increase with a rise in levels and development of 

 the reservoir function of the lake might have been expected. 

 There is, therefore, no January-February rise in the lake cor- 

 responding to that in the river unless the increase from .003 

 Jan. 11 to .04 Jan. 25 be held to be significant. The February 

 flood, which depletes the plankton of the channel, is accom- 

 panied by a rise to .58 on the 22d in the lake coincidently with 



