1916] 



Notes from the Woods Hole Laboratory — 1915 



91 



its vegetative and reproductive vigor that it is not perfectly at home 

 in this region. It has been previously reported 1 from Ireland, 

 Norway, Sweden, Denmark, France, and Silesia. 



During June and the first half of July it was found on only one stone. 

 Later in the season, 

 however, it had spread 

 to other suitable spots 

 in the neighborhood of 

 the Spindle, and seemed 

 to be in a fair way to 

 become generally dis- 

 tributed. It forms a 



Short dense turf, which Fl( . L _ p rasi<(la gtipiuta, mature plant. A, regions 



Seems at first sight to of akinete formation and liberation, h, holdfast. X 20. 



be composed of small Monos- 

 troma plants. The turf forms 

 green patches a foot and more 

 in diameter on the surface of the 

 boulders. 



The habit of the plant is char- 

 acteristic, very much like Mo- 

 nostroma except that it is from 

 the beginning filamentous and 

 is never saccate. Several fronds 

 arise from a single base (fig. 1). 

 Reproduction was found to be 

 entirely by means of akinetes, as is characteristic of the family of 

 Prasiolaceae. This method of reproduction was general and effective. 

 From the standpoints of multiplication and dissemination of the spe- 

 cies, the akinetes seem to be as efficient as the zoospores of the nearly 

 related Ulvaceae. The akinetes are formed in large areas covering 

 the ends of the fronds (fig. 1, A), and in these areas every cell is 

 involved. The cells here cease to divide, and become less clearly 

 green. At the same time the walls become swollen and softened. In 

 this condition the walls dissolve along their outer faces, though the 

 side walls persist for some time. Dissolution of the walls allows the 



apQDQP 



UcPwo 



aaao 



Fig. 2. — Prasiola stipita'ta. A. small por- 

 tion of thallus, showing cells in rows. B, C, D, 

 stages of akinetes. X 410. 



i De Torn, Sylloge Algarum, Pa via, 1889, Vol. 1, p. 145. 



