342 
The Philippine Journal of Science 
1914 
* 10. POTAMOGETON M AACKIAN US A. Benn. in Journ. Bot. 42 (1904) 74. 
Potamogeton serrulatus Regel & Maack in Regel Tent. FI. Ussur. (1861) 
139, non Schrader, nec. Opiz. 
Potamogeton crispus Linn var. serrulatus Schrad. “Japan” ex Science 
College, herb. Kew. ! 
Potamogeton Robbinsii Oakes var. japonicus A. Benn. in Bull. Herb. Boiss. 
4 (1896) 257. 
Mindanao, Lake Lanao, Camp Keithley, Mrs. Clemens 216, February, 
1906, growing with P. malaina. 
Distr. Ussuri, Regel & Maack! Mandschuria, Taladschao, Litwinow 
3346! Corea, Nai piang, Faurie 693! July, 1901. China, Yangtsee River, 
Warburg 5940 teste Graebner. Formosa, Warburg 10712, teste Graebner. 
.Japan, Faurie 10712, No. 44, 43 (1897) ! Hakone 1883, herb. Kew. 
The Asiatic representative of the North American P. Robbinsii Oakes! 
The species stands apart from any other, except P. Robbinsii Oakes, to 
which it is the nearest. The fruits are much alike in facies, but the 
leaves are quite different. The nerves are mostly 5 (against 18 to 24 in 
P. Robbinsii) and the structure of the leaf is totally different. In P. 
Robbinsii the marginal and central nerves are continued to the apex, but 
in P. Maackianus, on the contrary, the central nerve alone extends to the 
apex, the secondary nerves stop short, form an arch at the end, but the 
leaf is drawn in and continued beyond to an obtuse end. 
*11. X POTAMOGETON PHILIPPINENSIS nova hybrid =P. malainus X 
maackianus. 
Mindanao, Lake Lanao, Camp Keithley, Mary Strong Clemens, April, 
1906. 
A duplicate of this specimen previously examined by Dr. Ostenfeld and 
myself was thought to come nearest to P. nipponicus Makino, a Japanese 
species, but on receipt of the original specimen from the Bureau of 
Science and a comparison of it with Makino’s species, it became evident 
that it could not be so named. Both the supposed parents grow in Lake 
Lanao, and, short of the actual production of the hybrid by cultivation, 
I think it can only be so referred. Traces of both species are plainly 
visible, and of the two, it is doubtless nearer to P. malainus. The very 
peculiar intricate branching of the upper part, with the stipules, shows 
characters of P. Maackianus. There are no flowers or fruit with the speci- 
men. The habit is between that of malaina and that of Maackianus. Stems 
branching, and, toward the top, much branched with stiff, densely arranged 
patent leaves, with extremely short internodes, the stipules filling up the 
spaces. Lower leaves linear-lanceolate, the apex with a point drawn out 
about 8 mm, 4 cm long, 8 to 15 mm wide. Here and there a leaf shows an 
approach to the apical condition of those of P. Maackianus. Leaves on the 
crowded upper branches 3 cm long, 6 mm wide, mostly incurved and simi- 
rigid. Stipules persistent but mostly frayed. Leaves 5-nerved, with a 
strong mid-nerve. 
*12. POTAMOGETON PUSILLUS Linn. Sp. PI. (1753) 127. 
Luzon, Subprovince of Benguet, Baguio, Elmer 5951, in shallow stagnant 
water, common where found. 
The nearest recorded stations seem to be Formosa, Faurie 530 pp. (1903) ; 
