T}}c Plaiiktoi Algae of flic Palisades Interstate Park T17 



map is l)ased is more in the nature of a reconnaissance survey than a 

 thorough examination of the region, and it may be that there are 

 other small patches of sedimentary rocks like that near Popolopen 

 Pond. That there may be factors influencing the chemical com- 

 position of the waters of these lakes that do not have a rich desmiil 

 flora is suggested by the occurrence of blue-greefi algae in consider- 

 able quantit}- in Alombasha Lake and Long Pond. 



In seeking for an explanation for the correlation of the desmid 

 type of lake with the geological formations of a region W. & G. S. 

 \\'est have commented upon the absence of lime. Calcium and 

 magnesium seem to me to be important factors governing the dis- 

 tribution of desmids. LTn fortunately the artificial cultivation of 

 desmids is extremely difBcult, and there are no accurate data on 

 the mineral requirements of the family as there are in the case 

 of the other algae. The only investigation on the subject, that 

 of Andreesen ('09), sheds little light on the inorganic salts required 

 by these organisms. The analyses of lake waters in this region 

 show that the mineral content is low (Table 2) and that the lakes 



Table 2. — Analyses of lake zi'afer in tJic incinity of tlie Park. 

 (From the Reports of the New York State Department of Health.) 



P.A.RTS PER Million' 



Cedar Pond 

 Reser\'oir 



Lake 

 Mombasha 



Cromwell 

 Lake 



Bog Meadow 

 Pond (near 

 Long Pond) 



46. 



25 



6. 



14 



40. 



II 



. 022 





.110 





23-4 



4 



II . 



3 



Total solids 



Loss on ignition 



Mineral residue 



Free ammonia 



.■\lbuminoid ammonia 



Total hardness 



Alkalinity 



018 

 052 



054 

 090 

 9 



004 



144 



should support a small plankton population in case of the one old 

 lake from the Precambrian region, while Mombasha and Cromwell 

 Lakes have more mineral matter. The sample from Cedar Pond 

 was taken from Cedar Brook some distance below Cedar Fond, 

 and may not represent the condition in the Pond. 



The absence of lime may be the factor which favors the develop- 

 ment of desmids, but this absence of lime does not show why, from 

 the qualitative standpoint, the Caledonian association contains so few 

 representatives of the blue-green algae nor v,'hy, if a lake will sup- 

 port a certain number of these Myxophyceae, they are practically 

 all Chroococcaceae and not equal numbers of all plankton genera. 

 Temperature has been suggested as the factor limiting the production 

 of blue-green algae in the British lakes, but the temperature 

 of the Park lakes is the same as that of other lakes of the region 

 where ^Ivxophvceae are found in abundance, so that we cannot 



