190 Chaetophoraceae 



conjugation of the large and small gametes of the former to the 

 oogamous fertilization of the latter. 



I. MICROTHAMNION Nageli ; Kiitz. Spec. Alg. 352. 1849. 

 Kirchn. Krypt. Flor. Schles. 2 ! : 70. 1878. Borzi, Nuova. 



Notarisia, 2 : 390. 1891. Schmidle, Hedwigia, 38 : 165-170. 



1899. 



Thallus minute, attached by a bulbous basal cell, much 

 branched. Branches throughout of about the same diameter as 

 the main stem. In the formation of a branch, a growth is pushed 

 out at the upper end of a cell and the wall of separation is formed, 

 not at this point, but some distance above in the branch. Cells 

 cylindrical, the cell-wall very thin. Chromatophore a thin sheet, 

 more or less completely covering the cell-wall, without pyrenoids 

 but containing oil-drops. 



Asexual reproduction through zoospores formed in any cell 

 (the basal excepted) to the number of 4 or 8 ; they are ovoid in 

 shape, biciliate, without eye-spot, and germinate (apparently) 

 directly after adhering to a substratum, without rhizoid formation. 



Inhabitants of fresh water. Type M. Knetzingiamun Nag. 

 [Etym. [xcxpoQ, small, and dafivtov, a little bush.] 



This genus has frequently been placed in close relation to 

 Trentepohlia [e. g., by Wille in Die naturlichen Pflanzenfamilien), 

 because it has been supposed to have special terminal sporangia. 

 In all the forms, however, with which we are familiar, any cell in 

 the plant may produce zoospores, and with less swelling of the 

 filaments than in most of the Chaetophoreae. We have often 

 seen many of the lower cells of a branch hyaline from the loss of 

 the zoospores, before they have escaped from the terminal cells. 

 Hence the genus must occupy a position near to Myxonema. The 

 remark of Chodat ('02) " Borzi pretend avoir vu les zoospores 

 biciliees (4—6/^)" is unnecessarily discourteous, as there was every 

 reason to expect that zoospores would be found in these plants. 

 Equally unjustifiable is his placing this genus in the Pleurococ- 

 caceae. 



Synopsis of Species 



Ramification dense, without distinction between main stem and branches. 



1. M. Kueizivgianwu. 

 Ramification more open, erect, the main stem distinguishable to the summit. 



Terminal cells not narrowed. 2. M. strictissimum. 



Terminal cells slightly tapering. 2b. M. strictissimum macrocystis. 



