180 FRESH-WATER ALG^ OF THE UNITED STATES. 



spores possess, however, a peculiarity entirely distinct from 

 seeds and spores of other plants ; they multiply and renmltiply 

 and yet retain the character of spores. The provision appears 

 to be to prepare a bed, or soil, to sustain and nourish the forth- 

 coming comparatively few which do develop. 



In a paper read before the New York Microscopical Society, 

 by E. B. South wick (See Jour, of the Socy., Vol. 2, ~No. 1), 

 the writer observes on the frequency of Protococcus viridis. He 

 gathered it from the trunks of a hundred different species of 

 trees in Central Park, New York, some of the woods appearing 

 more favorable to the multiplication of the cells than others ; in 

 some cases the green coating, mostly on the north side of the 

 trees, extended up the trunk some distance ; on others it was 

 confined to the base ; some had very little, because not so well 

 adapted to its growth. He observes, "on the American Elm 

 the growth is most luxurious, extending to a great height." 

 1 ' On the Hibiscus the growth was of the finest character, and 

 hyphae were observed in a budding process having from 2-6 

 branching cells ; below, the hyphae were the large masses of 

 Protococcus cells which had been produced by fission, mostly in 

 twos and fours, standing out in projecting clusters. 



On the Hemlock it was very abundant and of a bright yellow- 

 ish green, and the gelatinous mass was so strong that when 

 placed under the cover-glass of a slide, in water, they were with 

 difficulty separated." 



Have quoted these words to indicate some of the different con- 

 ditions in which this arrested form of growth is found, and also 

 to indicate how a commencement of development into filaments 

 takes place. Had Mr. South wick continued his observations on 

 the hyphae at the base of the Hibiscus, where there is more 

 moisture, he would no doubt have discovered a development of 

 Ulothrix parietitia, Kg. 



These polymorphic (dimorphic; forms of arrested growths, 

 PROTOPHYTA, may, if at all deserving of a place in a system of 

 classification, be divided into two sections; the AERIAL and 

 the AQUATIC forms. 



It seems but natural that a plant-form developed in the water 

 will assume features differing more or less from those growing 

 out of the water. The land forms have usually thinner or some- 

 times crustaceous membranes, but even these after a rain or 

 during moist weather become gelatinous, thus indicating a 

 character which, when in the water, often produces a wide 

 hyaline envelope.. All the aquatic forms are larger than the 

 aerial varieties. 



