516 University of California Puhlications in Botany [Vol. 8 



The Pimctaria tenuissima Grev. is probably identical with P. undulata 

 J. Ag., now generally referred to Desmotrichum. 



It is much more difficult to determine the exact status of Pimctaria 

 plantaginea (Roth) Grev. The original is the plant figured in Dil- 

 lenius (1741, pi. 9, fig. 4) which, as well as the description, was 

 founded on a plant studied by Micheli. Smith (1810, pi. 2136) again 

 figured it and described it from Micheli 's material and notes which 

 had been communicated to him by Professor 0. Targioni-Tozetti long 

 after the death of Micheli. Whence the original material was derived 

 is uncertain, but it seems likely to have been the Adriatic Sea since 

 Micheli lived at Florence. In such a case, it is probable that it is not 

 the species which Greville referred to his Punctaria. plantaginea but 

 nearer to P. latifolia Grev. There seems to be little reason for doubt- 

 ing that the Pimctaria plantaginew as Greville understood it is also a 

 Punctaria^ in the sense of J. G. Agardh (loc. cit.). 



J. G. Agardh has proposed a segregate from Punctaria, viz., 

 Homoeo'stroma to receive the plant from Cherbourg, described and 

 figured as Punctaria- latifoUa by the French phycologists, Thuret and 

 Bornet (1878,p . 13, pi. 5). Whereas both the Punctaria latifolia and 

 the P. plantaginea of Greville have the external layer on each surface 

 of the frond distinctly smaller and more deeply colored than the 

 internal layers, in the P. latifolia of Thuret and Bornet (but not of 

 Greville) the external layers are of the same sized cells as those of the 

 interior and slightly, if at all, more deeply colored. In our experience, 

 however, there are forms difficult of placing in case Punctaria and 

 Homoeostroma are considered separate genera. 



There remain for consideration the relations of Punctaria and 

 Desmotrichiim. Kuetzing (1845, p. 244) founded the latter genus on 

 D. balticum, a slender, yet membranaceous form with hairs borne 

 singly and gametangia conical and practically superficial, at least 

 judging from his figures (Kuetzing, 1843, pi. 20 II, figs. 2, 4, 5-8). 

 Reinke, however, considers Kuetzing 's D. halticum to be a mono- 

 siphonous species although rarely it may be two to four cells wide, 

 while D. undulatum (J. Ag.) Reinke is the broader species. Aside 

 from the slender character of the frond, the strongly projecting or 

 even superficial gametangia and the hairs borne singly seem to dis- 

 tinguish the genus. We find, however, strongly projecting, even 

 superficial gametangia in broad species with hairs in groups. We also 

 find certain delicate, but broad species with single, promptly deciduous 

 hairs, and we find species in which there is no indication of hairs, 



