4 INTRODUCTION. 



and like it cut up by numerous ditches, in which are pretty much the same forms 

 as in the "Neck." But by taking the Camden and Atlantic cars for twenty to 

 forty miles into New Jersey to what is known as the " Pines," he will get into a 

 very different country ; low, marshy, sandy grounds, with innumerable pools, and 

 streams whose dark waters, amber-colored from the hemlock roots over which they 

 pass, flow sluggishly along. I have been, somewhat disappointed in my collections 

 in such localities. Fresh-water algse do not appear to flourish in infusion of hem- 

 lock, and consequently the streams are very bare of low vegetable life. On the 

 other hand, in pools in the more open places, my search has been repaid by find- 

 ing some very curious and interesting forms, which apparently are peculiar. 



North of Philadelphia are several places, which at certain seasons will richly 

 reward the microscopist. Along the Delaware River, there is a similar country 

 and flora to that of the " Neck." But back from the river things are quite dif- 

 ferent. The North Pennsylvania Eailroad passes near Chelten Hills, some eight 

 miles or so from the city, through some deep rock cuttings, which are kept con- 

 stantly dripping by numerous minute springs bursting from between the strata. 

 At the proper season, these will yield an abundant harvest. Besides these, there 

 is also a stream of water with ponds running along by the road, which should be 

 looked into. I have seldom had more fruitful trips than some made very early in 

 the spring to this locality; but then it was in little pools in the woods, and espe- 

 cially in a wooded marsh or meadow to the left of the road, some distance beyond 

 the station, that I found the most interesting forms. 



The Schuylkill River and its banks have afforded materials for many hours of 

 pleasant work. In the river itself a few very interesting forms have been found ; 

 but it is especially along its high banks that the harvest has been gathered. 



The dripping rocks and little wood pools in the City Park are well worth visiting; 

 but the best locality is the western bank, along the Reading Railroad, above Mana- 

 yunk, between it and the upper end of Flat Rock tunnel. Down near the river, at 

 the lower end of the latter, will be found a number of beautiful, shaded rocky pools, 

 which, in the late summer, are full of Chaetophora and other algse. Along the 

 west rocks of the river side of the bluff, through which the tunnel passes, are to 

 be found, late in the fall, numerous algse. It is here that the Palmella Jessenii 

 grows in such abundance. 



West of the city, in Delaware and Chester Counties, is a well wooded and 

 watered, hilly couhtry, in which, here and there, numerous fresh-water algse may 

 be picked up. 



As to the preservation of the algse — most of the submerged species are spoiled 

 by drying. Studies of them should always, when practicable, be made whilst fresh. 

 Circumstances, however, will often prevent this, and I have found that they may 

 be preserved for a certain period, say three or four months, without very much 

 change, in a strong solution of acetate of alumina. 



An even better preservative, however, and one much more easily obtained, is 

 carbolic acid, for I have studied desmids with great satisfaction, which had been 

 preserved for five or six years in a watery solution of this substance. In regard 

 to the strength of the solution I have no fixed rule. Always simply shaking up 



