Wittrockiellaeese 



311 



The Trentepohliacese are a somewhat specialized family of the Ulo- 

 trichales related to the Chsetophoraceae possibly through such forms as 

 Gongrosira in the Microthamniese. The simplest known type is Trentepohlia 

 umbrina (Kiitz.) Bornet, but this is doubtless a reduced form. The transition 

 from Trentepohlia to Phycopeltis is seen in those species of Trentepohlia 

 belonging to the section ' Heterothallus ' of Hariot, and from Phycopeltis to 

 Cephaleuros in the section ' Hansgirgia' of the first-named genus. 



Family Wittrockiellacese. 



This family was established by Wille to include the genus Wittrockiella 

 described by him in 1909. The thallus consists of erect and slightly branched 

 filaments (fig. 204 A) embedded in a tough mucilage derived from the outer 



D 



A. 



Fig. 204. Wittrockidla paradoxa Wille. A, vegetative thread with short branches ; B, germinating 

 akinete which has developed a hair-cell ; C, single cell fixed and stained to show the reticulate 



chloroplast with many pyrenoids (with double contours and seven nuclei (darkly shaded)) ; 

 D, formation of aplanospores ; E, formation of a large akinete. A and B, x 123 ; C, x 530 ; 

 D and E, x 240 (after Wille). 



layers of the cell-walls. The branches are few, often unicellular, and they 

 arise from the upper ends of the cells. Numerous thalli are agglutinated 

 to form a cartilaginous stratum on ground which is inundated by salt or 

 brackish water. The cells are mostly inflated, generally globose or ellipsoid, 

 rarely subcylindrical, and often rather irregular. The longest cells are those 

 in the basal part of the stratum and from these cells branches grow down- 

 wards to form multicellular rhizoids. From the upper cells hairs are 

 developed. These attain a considerable length, extending beyond the 



