June 18, 1869.] 11" [ Wood . 



PRODROMUS OF A STUDY OF THE FRESH WATER ALGAE 

 OF EASTERN NORTH AMERICA. 



By Horatio C. Wood, Jr., 



Professor of Botany in the University of Pennsylvania. 



For several years all the leisure, my more strictly professional duties 

 allow me, has been devoted to the study of the Alga-fauna of our inland 

 waters, and I had intended delaying publication until ready to offer to 

 the scientific Avorld an elaborate memoir upon the subject. Tlie field is 

 however so constantly enlarging, that the day of final preparation seems 

 rather to recede than draw near. This and the hope of stirring up other 

 laborers, have induced me to print now a very brief abstract of tlie results 

 that have so far rewarded my efforts. In enumerating and describing the 

 species herein contained, I shall follow the classification and arrangement 

 adopted by Rabenhorst in his ' ' Flora Europoea Algarum. ' ' It should, 

 however, be plainly understood that I do not do this, as endorsing the 

 method of the German Professor, but simply because I do not feel pre- 

 pared at present to discuss the natural arrangement of this group, and 

 desire to leave the whole subject for a future Memoir. 



The desire of enlisting the assistance various of observers, as already 

 mentioned, has been one of the motives that have prompted me to publish 

 at this time. I am already greatly indebted to several botanists for aid, 

 amongst whom I may mention Dr. J. S. Billings, U. S. A., Professor H. 

 W. Ravenel, and Mr. William Canby, and am thereby emboldened to ask 

 for more . If there are any persons engaged in the study of these plants, I 

 will be most happy to exchange specimens with them, eitlier fresh or 

 mounted for the microscope ; and when occasion may arise, will most 

 freely give all the credit due them for species new to America or Science, 

 If there are others willing to help me, I will do all in my power to aid 

 them in return by labelling specimens, giving information as to books, 

 &c., or make such other returns as circumstances will permit. Any one 

 who is thus willing had better address me by letter, when I will forward 

 to him preservative fluid, with some directions. 



A certain amount of experience and knowledge of the subject greatly 

 facilitates the collection of these plants, but scarcely so much as in other 

 departments of cryptogamic botany. Most of the species of fresh water 

 algae are so small that the most experienced algologist does not know 

 how great the reward of the day's toil may be until he places his booty 

 on the object glass of his compound microscope. In order to aid any one 

 who is desirous of collecting and studying these low forms, it seems to 

 me not amiss to make here a few remarks upon the where and the when 

 to look, and the how to preserve after they are found . 



There are three or four distinct classes of localities, in each of which a 

 distinct set of forms may be looked for. Stagnant ditches and pools ; 

 springs, rivulets, large rivers, and other bodies of pure water ; dripping 

 rocks in ravines, &c.; trunks of old trees, boards, branches and twigs of 

 living trees and other aerial localities. 



A. P. S. — VOL. XI — P 



