INTRODUCTION. 3 



In regard to large rivers, the time of year in which I have been most successful 

 in such localities is the latter summer months. Springs and small bodies of clear 

 water may be searched with a hope of reward at any time of the year when 

 they are not actually frozen up. I have found some exceedingly beautiful and 

 rare algse in such places as early as March, and in open seasons they may be col- 

 lected even earlier than this. The desmids are most abundant in the spring, and 

 possibly most beautiful then. They, however, rarely conjugate at that time, and 

 the most valuable specimens are therefore to be obtained later — during the summer 

 and autumn months ; at least, so it is said; and the experience I have had with this 

 family seems to confirm it. Rivulets should be watched especially in early spring, 

 and during the summer months. 



From the time when the weather first grows cool in the autumn, on until the cold 

 weather has fairly set in, and the reign of ice and snow commences, is the period 

 during which the algse hunter should search carefully all wet, dripping roclcs, for 

 specimens. Amongst the stems of wet mosses — in dark, damp crevices, and little 

 grottos beneath shelving rocks — is the algse harvest to be reaped at this season. 

 Nostocs, palmellas, conjugating desmids, sirosiphons, various unicellular algse, then 

 flourish in such localities. My experience has been, that late in the autumn, 

 ravines, railroad cuttings, rocky river-banks, &c., reward time and labor better than 

 any other localities. 



The vaucherias, which grow frequently on wet ground, as well as submerged, 

 fruit in the early spring and summer in this latitude, and are -therefore to be col- 

 lected at such times, since they are only worth preserving when in fruit. 



In regard to algse which grow on trees, I have found but a single species, and do 

 not think they are at all abundant in this latitude. Farther south, if one may 

 judge by Professor Eavenel's collections, they are the most abundant forms. 



Although perhaps of but little interest to the distant collector, yet for the sake 

 of those living nearer, I will occupy a few lines with an account of the places 

 around Philadelphia which will best repay a search for fresh-water algse. As is 

 well known, below the city, there is what is known as the "Neck," a perfectly level 

 extent of ground lying in the fork between the rapidly approaching rivers, Schuyl- 

 kill and Delaware. This is traversed by numerous large ditches, and, especially 

 just beyond the city confines, has yielded to me an abundant harvest. My favorite 

 route is by the Fifth Street cars to their terminus, then across the country a little 

 to the east of south until the large stone barn, known as " Girard's Barn," is 

 reached. A large ditch lies here on each side of the road, which is to be followed 

 until it crosses the Pennsylvania Railroad, then along this to the west, until the 

 continuation of Tenth Street crosses it. Here the ditches cease, and the steps are 

 to be turned homeward. From Girard's barn to the crossing just alluded to, 

 ditches great and small lie all along and about the route, ditches which have often 

 most abundantly rewarded my search, and enabled me to return home richly laden. 

 The best season for collecting here, is from March to July, and again in October, 

 when some of the nostocs may be looked for. 



Crossing the river Delaware to the low country below and above the city of 

 Camden, the collector will find himself in a region similar to that just described, 



