LINDMAN, AMERICAN SPECIES OF TRICHOMANES SM. 11 



we find vague or imperfect descriptions; and as they are not 

 illustrated at all, these species of microscopic plants must be 

 disregarded l)y subsequent authors, who can not obtain the 

 original specimens. 



It seems necessary to give a safe and incontestable foun- 

 dation to the oldest species, before we can arrive at anj' cer- 

 tain knowledge of the more recent ones. I believe the best 

 method for this purpose is, to start from authentic specimens, 

 or original descriptions which are combined with an illustra- 

 tion, and not to spare any trouble in searching for the va- 

 rious forms of the pol^nnorphous plants, which should be 

 drawn all on a fixed enlarged scale together with a sketch 

 of the cellular structure. For my part, I am convinced that 

 no words can give a fully accurate and clear idea of these 

 small plants, which evidently have a tendency to change, in 

 various directions, a simple primitive type into very many 

 closely allied forms, as we are taught by the ever increasing 

 number of new species. 



My illustrations are all drawn by the aid of the micro- 

 scope and Zeiss's camera lucida, and then painted with In- 

 dian ink; the enlargement was originally 2 or 3 times greater 

 than the illustrations, published, which are consequently as 

 much reduced again to ^2 or V/s from the original painting. 



I describe first Swartz's Trich. nniscoichs, but as this 

 author has himself quoted Trichonmnes hymenoides Hedwig, 

 Pilicum genera et species, 1799, tab. IV, fig. 3, and nothing 

 contradicts this, I accept hymeiwides as the oldest name. 



By the side of several well known species, I describe 

 here a few new ones. The species I am now about to deal 

 with, all belong to the genus (or subgenus) Pidymogrlossuin 

 Desvaux, for which the author^ has given as generical 

 marks: 



;Sori marginales exserti; sporangia sessilia receptaculo 

 communi cylindraceo inserta; involucrum urceolatum ore 

 hiante biligulatum.v 



* Desvaux. in Mémoires de la Société Linnéennc de Paris. 6 (.1827 — 28). 

 I). ^töO: 3 species, viz. mnscoides (Sw.), pusillum (Sw.), punctatum (Poir.). 



