FIFTH REPORT OF THE DIRECTOR I908 



205 



system) at Minneapolis that contains numerous fragments of the 

 thallus of an exceedingly delicate alga easily mistaken for a grap- 

 tolite on account of the regularity of its structural features. 



The specimens are very slender and preserved only as a brown, 

 mostly thin film, wttiich, however, shows very plainly under water 

 or glycerine. Occasionally also thicker carbonaceous portions are 

 observable. They consist essentially of a uniformly thick or very 

 gradually tapering main axis and regularly arranged whorls of very 

 thin, filamentous branches which from their position in all speci- 

 mens observed, would seem to have sharply bent upward outside of 

 this thickened base and grown subparallel to the main axis. There 

 were six or more in one whorl. No conclusive traces have been 

 seen in the main axis of either transverse walls, indicating a 

 segmentation or articulation, or of longitudinal walls suggesting 

 a composition of thecal tubes of graptolitic character. 1 The absence 

 of the latter partitions is also suggested by the smooth outside of 

 the main branch. 



On account of the arrangement of the branchlets in close whorls 

 on the main branch and the absence of a further division of the 

 branchlets, either by bifurcation or formation of whorls, this species 

 is best brought under Chaetocladus, although it will be noticed that 

 it represents a transitional form between the extremely densely 

 whorled Chaetocladus p 1 u m u 1 a Whitfield that possesses 

 hardly any further division and C a 1 1 i t h a m n o p s i s d e 1 i c a - 

 tula that possesses like whorls on the main branch but also a 

 further subdivision of the branchlets that gives it the habitus of a 

 Callithamnopsis. 



The most interesting feature of Chaetocladus sardesoni 

 consists in the bulbous swellings of the bases of the branchlets 

 forming the annuli around the main branch. These bulbs are seen 

 in several specimens to have been hollow and to be formed by 

 thicker tissue [see pi. 2, fig. 9]. They may therefore possibly 

 have contained sexual or nonsexual propagative organs and corre- 

 spond to conceptacles observed in some Florideae in a similar 



position. _ , , 



Corematocladus gen. nov. 



Ety. Kuprifia = a broom, KAddo$ — a young branch 

 Thallus composed of thick subcylindric stem that is sur- 

 rounded by a dense mass of filamentous, frequently subdividing 

 branches. Genotype, Corematocladus den sa sp. nov. 



'In regard to this observation we have t<> rely mainly on the natural sec- 

 tions produced by the splitting of the stem through the middle since thin 

 sections failed on account of the flattening of the stem to reveal distinct 

 structures. 



