-8 3 - 



ments. Torka does not state whether these plants produced sporophytes or 

 not. In 1914 he distributed excellent specimens of his var. natans (9, No. 51) 

 from the Zablocie locality. These present the appearance of a slender aquatic 

 R. fluitans, as this species is usually understood. 



It is unfortunate that Torka 's evidence is not more conclusive. Although, 

 in his cultures, the tips of the thalli often detached themselves and floated on 

 the water, nothing is said about their growing while in this condition. It is 

 implied, in fact, that the floating fragments carried on a very precarious existence 

 unless they came in contact with some firm substratum. The mere fact that 

 they remained green for a while would hardly show that they represented a 

 true aquatic form of R. Huebeneriana. In order to prove that such a form had 

 been produced it should have been shown that the plants in question were cap- 

 able of continuing their growth and development in their new environment. 

 With regard to the Polish specimens of his var. natans the evidence is lacking 

 that these actually represent R. Huebeneriana. The only way in which this 

 could be proved would be by means of morphological characters either in the 

 thallus or in the spores. No such characters are given, and, although the attached 

 plants are said to resemble the attached fragments of R. Huebeneriana in the 

 water cultures/these fragments (as represented by Torka 's figure) are hardly 

 representative of R. Huebeneriana as it normally appears. The case is further 

 weakened by the fact that he does not report the normal terrestrial R. Hueben- 

 eriana in the vicinity of the var. natans, although he cites a single station for 

 it at a somewhat distant Polish locality. 



In 19 1 6 Donaghy (1) published a series of interesting field observations 

 on R.fluitans, as it occurs in Indiana. He reports that the so-called terrestrial 

 form is uncommon in his region but notes its occasional appearance "on mud 

 flats and wet fields during the autumn." This form produces sporophytes in 

 abundance. The aquatic form is abundant around Angola, Fort Wayne, and 

 Terre Haute, where "during the summer and autumn mats .... can be 

 found floating in ponds and sluggish streams, "sinking to the bottom in the winter 

 and remaining there until spring. Although plants beneath the ice remain un- 

 injured, those "frozen in the ice are much winter-killed, the apical ends alone 

 remaining green." During "spring these plants make rapid growth, and by 

 summer patches of thalli again dot the ponds and streams." When, owing to 

 evaporation, the water becomes low, "mats of plants are" often "washed upon 

 the wet edges of the ponds, " and "in favored places the thalli coming in contact 

 with the wet soil develop rhizoids .... and open air-chambers." Whether 

 such plants ever develop sexual organs and sporophytes remained uncertain, 

 Donaghy 's evidence on this point being wholly negative. He reports a case 

 where plants "remained alive in wet shaded places .... in contact with the 

 earth sufficiently long to fruit," and yet "no sporophytes were formed." 



In Donaghy 's opinion these sterile terrestrial plants, derived from the 

 aquatic plants, were distinct from the so-called terrestrial form of R. fluitans, 

 and he failed to find the latter on the mud of ponds where the aquatic form was 

 growing. He concludes from his observations that "it seems very doubtful 



