F. Børgesen: List of species. 451 



From the spore a few cells are gradually developed in all 

 directions; by more or less growing together they form in older, 

 vigorous plants a small disc. From the spore and from the sur- 

 rounding cells erect filaments are given off. These are mostly 

 not ramified near their base, higher up branches are given off in 

 all directions. 



At the base the filaments are 8 — 10 — 12 fi broad, tapering 

 slowly upwards, the apices reaching a breadth of about 4 — 6 n 

 only. The filaments reach a height of about 3 mm. The cells contain 

 a parietal, slightly developed chromatophore with a lateral pyre- 

 noid protruding far into the cells. The chromatophore is mostly 

 developed in the basal part of the plant, upwards less so. The bran- 

 ches are given off at acute angles in all direction from the main 

 filaments which are for the most part easily observable; the bran- 

 ches are similar to the main filaments, thicker below, thinner 

 upwards. At their base from the distal end of the lowermost cells 

 the sporangia are issued (Fig. 419 c). These are sessile or pedi- 

 cellate, in some specimens about half of all the sporangia are 

 pedicellate. The sporangia have a little thickening of the wall 

 in their upper end' (Fig. 419 d). They are about 11 — 12 fx broad 

 and 21 ^ long. Other fructiferous organs were not found. 



If we now compare this plant with the above-mentioned 

 four related species and begin with Acr. unipes we find, that this 

 species differs firstly by the fact that generally a single erect fila- 

 ment is issued from each spore; now and then an accessoric branch 

 may be present, but this is no doubt mostly due to the fact 

 that the primary branch has been damaged; comp, my fig. 33 b. 

 The sporangia seem always to be sessile in Acr. unipes, and they 

 are more scattered placed upon the branches; furthermore the 

 sporangia are proportionally a little broader in Acr. unipes, namely 

 about 12// broad and 20 fi long, and their apex is more obtuse 

 with no such marked thickening above in the wall. 



According to Howe's and Hoyt's description Acr. affine 

 differs from our plant on account of the 1 — 4 erect filaments 

 issuing from the primary basal cell, "often subdichotomous or 

 subtrichotomous at the distal end of the first cell"; further- 

 more by the presence of terminal hairs. Cystocarps and anthe- 

 ridia were found in this plant. 



And Acr. robustum differs from the above described form 



29* 



