78 
Bristol. — On the Alga-Flora of some Desiccated 
The following is a diagnosis of this new species : 
G. terricola , in solo culto vigens, stratum expansum efformans ; thalli 
pars inferior e filamentis densis ramosis, cellulis tumidulis subglobosis vel 
irregularibus constat, pars superior e filamentis erectis fasciculato- vel 
pseudodichotomo-ramosis apicem versus angustioribus, cellulis subcylindricis 
tumidulis vel irregularibus. Cellulae inferiores 11 to i6/x crassae, cellulae 
filamentorum erectorum 6 to 14/x latae, 10 to 18/x longae, cellulae apicales 
obtusae non attenuatae, omnes chromatophoro irregulari parietali, pyrenoidi- 
bus singulis (rarissime binis) vel nullo instructae. 
Zoogonidangia basalia vel intercalaria subglobosa vel ovoidea, 14 to 18 /x 
crassa, ore minuto laterali dehiscentia. 
Hab. in solo culto Kettering (Northants), Baggeridge (Staffs.), Tisbury 
(Wilts.). 
18. Tribo7iema bombycinum , (Ag.) Derb. and Sol. (Text- fig. 5). 
This species was found in the cultures of four different soils, and in 
most cases was quite typical in character, with slightly tumid cells, 8-5 to 9 /x 
broad by 18 to 21 /x long, and cell-walls breaking into H -shaped pieces in 
the fragmentation of the filament. Multiplication by means of zoogonidia 
was not observed in the cultures, but aplanospores were formed as described 
at the end of Section III of this paper. 
19. Bumilleria exilis , Klebs. (Text-fig. 1). 
This alga, though never previously recorded for the British Islands, was 
found in forty of the soils, and is evidently a typical soil-species, since it was 
originally described by Klebs from a very similar habitat. Its appearance 
in the cultures seemed to be periodic ; its growth gradually attained to 
a maximum during the first eight months of the investigation, and in May, 
1916, it was the dominant form present in many of the cultures. From 
that time onwards it gradually disappeared until in the early months of 
1917 only a few isolated filaments could be found ; while six months later 
it had again increased in quantity in many of the cultures, though the 
second maximum never attained to the height of the first. 
The cells of the filaments were almost rectangular, with slightly tumid 
walls, and were usually about 4-5 /x broad. They varied in length from 10 
to 15 /x, sometimes less, and contained a variable number of small, parietal, 
yellow-green chloroplasts, four in the shorter cells and 6 to 12 in the longer 
ones; starch was never observed in them, but small globules of oil were 
often present. 
Multiplication took place most frequently by a fragmentation of the 
filament, either through the breaking of the wall of one of the cells into 
H -shaped pieces (Text-fig. 1, d), or more frequently through the splitting 
apart of the end walls of two adjacent cells (Text-fig. l,b), and the conse- 
quent formation of knee-bends. In a few cases the early stages of 
