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 differences 

 in the amount of chlorine undoubtedly influence to a considerable 

 extent the character of a flora. Then again the clearness of the 

 water, temperature, presence of currents, amount of sewerage, etc. 

 are factors which exert an intluence upon the distribution of aquatic 

 plants. Of the plants which require especial notice may be men- 

 tioned the following : Elodea Canadensis which fruits abundantly 

 every two or three years in Lake Quinsigamond is confined entirely 

 in central Massachusetts to this body of water and its adjacent 

 streams. Hypnum aduncum, hamatum, Chara hydropitys, Reich, 

 C. crinita Wallr, C. sejuncta, A. Br., as well as many of the Algae 

 have not been observed elsewhere in this region. Among the rare 

 Algae may be mentioned Craterospermum laetevirens, A Br. which 

 we have observed only in Lake Quinsigamond, and here in certain 

 localities it is found abundantly 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, 

 N. J. The conjugation was complete, but the spores were imper- 

 fectly developed, hence my hesitancy in calling it a pronounced spe- 

 cies of this genus." Abundance of the mature fruiting forms have 

 been observed in Lake Quinsigamond. 



Pleurocarpus mirabilis, A Br. an alga common everywhere, 

 although most always sterile, was obtained from a small brackish pool 

 abundantly in fruit in the summer of 1893. Wolle remarked that he 

 observed this form for eight years without ever finding it in fruit 

 and in 1883 he reports it as having been found fruiting in four dif- 

 ferent places by as many observers. 



It would be of some interest to ascertain whether such species are 

 subject to a definite 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 obser- 

 vations during 1890 extended throughout the whole season and we 

 were therefore able to pay some attention to the seasonal distribution 

 of forms. 



There are two such marked periods which may be termed the 



