142 MESSRS. W. WEST AND G. S. WEST ON 
Dr. Lauder's drawing of this species given by Archer (Quart. Journ. Micr. Sci. 1865, 
t. 7. fig. 2) is a poor representation of the plant, and as that was all Archer had to go by, 
his description is also not quite accurate. "There are no “ hyaline quadripartite spines,” 
the conical spines being arranged in pairs. The number of pairs of spines in each whorl 
varies considerably. Mr. Kaye informed Archer that there were 10 prominences in each 
whorl; Borge says 15—17 pairs of spines at the base, and 7-12 spines at the apex for his 
Docidium horridum. We find 12 in each whorl, including the apex. 
There is no question that D. horridum, Borge, is identical with D. Kayei, Arch. 
88. PLEUROTZNIUM ANNULATUM, West & G. S. West, in Journ. Bot. xxxvi. 1898, p. 332. 
Docidium annulatum, Joshua, in Journ. Linn. Soc., Bot. xxi. 1886, p. 651, t. 25. 
fig. 13. Docidiwm egregium, W. B. Turn. in K. Sv. Vet.-Akad. Handl. xxv. 1898, 
no. 5, p. 94, t. 2. figs. 14, 15. 
Long. 234-318; lat. ad bas. semicell. 18-20 4, lat. ad med. 17:5-18 u, lat. apic. 
13:5-16 u. 
Hab. Paddyfields, Heneratgodha. Paddyfield between Kosgoda and Urahaighasma- 
hendai. 
We have already shown that Docidium egregium, W. B. Turn., is identical with Pleuro- 
tenium annulatum, and also that its cell-wall possesses shallow internal pits. These pits 
are of a regular broadly-rounded form, and are not so well marked as those of 
P. trochiscum or P. doliforme, being almost invisible under a magnification of 250 
diameters. We take the opportunity of giving a careful drawing of one of Joshua’s 
Burmese specimens (Pl. 19. fig. 5) for comparison with a specimen from Ceylon (Pl. 19. 
fig. 6). 
89. PLEUROTZNIUM TROCHISCUM, West & G. S. West, in Trans. Linn. Soc., ser. 2, Bot. 
vol. v. 1896, p. 235, t. 13. figs. 4, 5. 
Long. 265—309 u; lat. ad bas. semicell. 20-26; lat. ad med. semicell. 17-22 „u; lat. 
apic. 16-19°5 „u. (PI. 19. figs. 7, 8.) 
Hab. Paddyfields, Heneratgodha.  Paddyfield between Kosgoda and Urahaighasma- 
hendai. 
Although the specimens from Ceylon were very variable in size, the largest did not 
equal in dimensions any of the American examples. In all cases the pitted marks were 
more regular towards the apices of the cells than in any specimen we have previously 
seen, and in some they showed a tendency to coalesce into annular bands. A few 
examples were noticed in which minute scrobiculations were present on the cell- 
wall between the pits, thus proving the close relationship between this species and 
P. annulatum. 
90. PLEUROTJENIUM DOLIFORME, Sp. n. (Pl. 19. figs. 9,10.) P. submagnum, diametro 
33—41-plo longius; semicellule ovato-doliformes, levissime productis apices versus, 
apicibus truncatis tuberculatis, tuberculis parvis 10 (visis 6) infra apicem ; membrana 
