inasmuch as the presence of these organ- 

 isms is now believed to possess some 

 economic importance. 



The Flora of Middlesex county appears 

 to be the only one that has included any 

 of the fresh water Algae peculiar to our 

 Massachusetts lakes and streams. 



In this work issued by Dame and Col- 

 lins there is given a total of 204 species 

 and varieties, some fifty of which are 

 either salt water species or common to 

 salt water marshes, thus bringing the 

 purely fresh water species down to about 

 150. With the exception of the Desmids 

 in this list, of which there are about eighty 

 specdes representing those determined by 

 Dr. Lagerheim, all of the fresh water 

 Algae were taken from Dr. Farlow's her- 

 barium. In the absence of extensive 

 studies of our fresh water Algae through- 

 out Massachusetts it is not possible there- 

 fore to make comparisons of the algal 

 flora of the different regions. That char- 

 acteristic differences exist in the flora of 

 our ponds and streams is evident to those 

 who have paid some attention to collect- 

 ing. We have similar environmental fac- 

 tors to deal with in considering an aquatic 

 flora as we have in a land flora. The 

 nature of the soil which constitutes the 

 lake or pond bottom is variable, both in 

 its mechanical and chemical composition, 

 and the chemical composition of the water 

 is by no means the same for different 

 localities. Chemical analysis has shown 

 that the amount of chlorine in Berkshire 

 county is .06 or .08 in parts per 100,000, 

 while that in the vicinity of Boston ranges 

 from about .35 to .65, and on Cape Cod 

 it reaches as high as 2.62. The differ- 

 ences in the amount of chlorine undoubt- 

 edly influence to a considerable extent the 

 character of a flora. Then, again, the 

 clearness of the water, temperature, pres- 

 ence of currents, amount of sewage, 

 etc., are factors which exert an influence 

 upon the distribution of aquatic plants. 

 Of the plants which require especial notice 

 may be mentioned the following: Elodea 

 Canadensis, which fruits abundantly every 

 two or three years in Lake Quinsigamond, 

 is confined entirely in central Massachu- 

 setts to this body of water and its adja- 



cent streams. Hypnum aduncum, hama- 

 tum, Chara hydropitys, Reich, C. crinita 

 Wallr, C. sejuncta, A. Br., as well as many 

 of the Algae have not been obsen^ed else- 

 where in this region. Among the rare 

 Algae may be mentioned Craterospermum 

 laetevirens, A. Br., which we have ob- 

 served only in Lake Quinsigamond, and 

 here in certain localities it is found abun- 

 dantly in all stages of development. 



Wolle remarks "That the only specimens 

 recognized as possibly belonging to this 

 genus were collected July, 1880, in Green 

 pond, X. J. The conjugation was com- 

 plete, but the spores were imperfectly de- 

 veloped, hence my hesitancy in calling it 

 a pronounced species of this genus." 

 Abundance of the mature fruiting form? 

 have been observed in Lake Quinsigamond. 



Pleurocarpus mirabilis, A. Br., an alga 

 common everywhere, although most al- 

 ways sterile, was obtained from a small 

 brackish pool abundantly in fruit in the 

 summer of 1893. Wolle remarked that he 

 obsei-ved this form for eight years with- 

 out ever finding it in fruit, and in 1883 

 he reports it as having been found fruit- 

 ing in four different places by as many 

 observers. 



It would be of some interest to ascertain 

 whether such species are subject to a defi- 

 nite periodicity in their fructification, or 

 whether they are dependent entirely upon 

 ecological factors. It is quite evident from 

 our own cultures of Algae that variations 

 in the environment have a considerable 

 bearing upon their fructification. Our ob- 

 servations during 1890 extended through- 

 out the whole season, and we were there- 

 fore able to pay some attention to the 

 seasonal distribution of forms. 



There are two such marked periods 

 which may be termed the maximum pe- 

 riods; one occuning in the spring, and 

 the other in the autumn. 



One of the most important factors 

 which determine the occurrence of species 

 is the height of the water. An increase 

 of one or two feet in the height of water 

 during the spring and summer months 

 over that of a normal season will com- 

 pletely shut out for that season many 

 forms of aquatic plants. During seasons 



