FRESH-WATER ALG^ OF THE "UNITED STATES. 79 



Remarks. — I am indebted to Mr. Austin for specimens of this little plant, which 

 he found growing in a swamp near Closter, Northern New Jersey, on a young 

 pin oak. It forms a sort of crustaceous powder, with little aggregations here and 

 there, of a dull reddish-brown color. When these little masses are broken up, 

 they are found to be composed of little series of very closely joined cells, generally 

 a half dozen to a dozen in the row. I believe that at certain states of their growth 

 these cells are green, as many of them have a very decided green tint on their 

 edges, and I have seen one or two of them quite green. 



Fig. 2, pi. 10, represents this species magnified 460 diameters. 



P. pulvereus; Wood, (sp. nov.) 



P. cellulis minimis, caeruleo-viridibus, enormiter subglobosis, vel angulosis, in familias nume- 

 rosas consociatis ; familiis e cellulis numerosslssimis et dense confertis compositis, irregu- 

 laribus, interdum confluentibus, plerumqne pseudotegumentis hyalinis involutis, in strato 

 pulvereo Isete viridi aggregatis. 



IHam,.—^l-^^'—^%^' = .00004"— .00013". 



Hab. — In fonte. " Boiling Springs," prope Bellefonte, Pennsylvania. 



Cells very small, bluish-green, irregularly subglobose, oval, or angular, associated in numerous 

 families ; families composed of very numerous and densely crowded cells, irregular, sometimes 

 confluent, mostly surrounded by a false hyaline tegument, aggregated into a bright green 

 pulverulent stratum. 



Remarhs. — In Centre County, Pennsylvania, two miles from Bellefonte, there is 

 a very large and beautiful limestone spring, which is a favorite roadside watering 

 place, and is laid down on the maps as " Boiling Springs." Forming a stratum 

 over most of the bottom of this spring is the little plant here described. The 

 stratum is in places nearly an inch in thickness, and when lifted by the hand is - 

 found to be dry and crumbly, instead of mucous and tenacious. Under the micro- 

 scope it is seen to be composed of vast numbers of irregular masses or families of 

 cells imbedded in a firm jelly, which projects so as to form a sort of transparent 

 coat to the whole mass ; this cast I have spoken of in the description as a false 

 tegument. The cells themselves are exceedingly small and furnished with an 

 excentric point, which is probably a nucleus. 



Genus PALMELLA. 



Cellulse globosse vel ovales vel oblongae, tegumentis plus minus crassis in mucum gelatinosum, 

 saepius mox confluentibus involutae, thallum difforme efficientes. Cellularum divisio directione in 

 omnes dimensiones alternante. 



Cells globose, oval, or oblong, surrounded with a more or less thick integument generally very 

 soon confluent into a firm or soft jelly. Thallus shapeless. Division of the cells alternately in all 

 directions. 



P. Jesenii, Wood. 



P. thallo indefinite expanso, initio dilute aut Isete viride, molle, pellucidulo ; aetate provecta 

 firmo, tuberculoso, saturate olivaceo-viride ; cellulis globosis vel ellipticis, — in thalli aetate 

 immaturo, plerumque singulis aut geminis, saepe distantibus, — in aetate provecta ssepe in fami- 

 lias connexis, plerumque confertis ; tegumentis in thalli aetate immaturo plerumque diffluenti- 

 bns, aetate provecta plerumque distinctis. 



