KEY TO THE BEITISH SPECIES. 93 



TOLYPELLA, 



Ultimate cell of the rays conical. Membrane of oospore 



extremely thin. 



Sterile branchlets furcate . . . 1. T. intricata* 



Sterile branchlets simple . . . 2. T. prolifera. 



Ultimate cell of the rays allaiitoid. Sterile branchlets 



simple. Membrane of oospore thick. 

 Ripe oospore small (c. 340 x 275 ju) ellipsoid, mem- 

 brane dull yellow to red . . . 3. T. glomerata+ 

 Ripe oospore large (c. 450 x 400 ju) subglobose, 



membrane wine-red .... 4. T. nidifica. 



NITELLOPSIS. One species. 

 LAMPEOTHAMNIUM. One British species. 



CHAR A. 



Haplostephanous, *. e. stipulodes in a single row. 



Stem ecorticate . . . . . . 1. C. Braunii*. 



Diplostephanous, i. e. stipulodes in a double row. 



Stem-cortex rudimentary (see also below) . 8. C. denndata.. 

 Stem-cortex haplostichous, i. e. having a single row 



of cortical-cells to each branchlet . 2. C. canescens. 

 Stem-cortex diplostichous, i. e. having two rows of 

 cortical-cells to each branchlet, a central 

 (primary) and a lateral (secondary). 

 Aulacanthous, i.e. secondary cortical-cells more 



prominent than the primary. 

 Posterior bracts usually rudimentary. Spine- 

 cells all solitary . . . . 3. C. vulgaris.. 



Posterior bract-cells developed. Spine-cells 



mostly two or three together. 

 Secondary cortical-cells much larger than the 

 primary. Spine-cells mostly geminate, 

 one above the other . . . 4. C. rudis. 

 Secondary cortical-cells not much larger than 

 the primary. Spine-cells mostly 2-3 to- 

 gether, when geminate usually produced 

 side-by-side . . . . 5. C. liispida. 



Tylacanthous, i. e. primary cortical-cells more pro- 

 minent than the secondary. 

 Dioecious. Spine- and bract-cells very broad. 

 Lowest branchlet-segment with ascending 

 cortex . 6. C. tomentosa. 



