II. Rachis of spikes narrow, filiform, terete or angular. First glume shorter than the third. First glume semilunate, about 1/4 of the third glume. 7. P. prostratum. First glume 1/2 of or less than 1/2 of third glume, 5-nerved. 8. P. ramosum. Leaf base broad or cordate. Fourth glume shortly awned. 9. P. javanicum. Fourth glume muticous. 10. P. distachyum. B. Inflorescence a contracted or open panicle. I. Panicle contracted and spike-like. Spikelets lanceolate and first glume minute. 11. P. interruptum. II. Panicle effuse. Annuals; first glume nearly 3/4 of the third glume. 12. P. trypheron. Perennials; first glume less than 1/3 of the third glume. 13. P. repens. [Illustration: Fig. 80.--Panicum Isachne.] =Panicum Isachne, _Roth._= This is an annual grass usually growing in tufts with fine fibrous roots and many slender spreading branches, all of them at first creeping and horizontal, rooting at the nodes and then becoming erect and varying in length from 1 to 2 feet. Stems are very slender, glabrous or covered with scattered hairs, purplish or pale green, and branching freely towards the base. The _leaf-sheath_ is shorter than the internodes, green or purplish, striate, externally hairy with scattered bulbous-based hairs, varying in length from 1/2 to 3 inches, the outer margin of the sheath is ciliate with long hairs and at the mouths sometimes long hairs are present, especially when the leaves are young. The _ligule_ is merely a dense fringe of long hairs. _Nodes_ are tumid, purplish, covered with long hairs. The _leaf-blade_ is flat but convolute when young, lanceolate or linear-lanceolate, acuminate, base rounded and margin with minute serrations. It is glabrous or occasionally hairy with scattered, tubercle-based, deciduous hairs, and varying in length from 1 to 3 inches generally (sometimes in well-grown plants it is 5 inches) and in breadth from 1/8 to 1/4 inch. The midrib is prominent though slender at the base and four veins are present on each side with five or six smaller ones between them. [Illustration: Fig. 81.--Panicum Isachne. 1 and 1a. Front and back view of a spike; 2 and 2a. back and front views of a spikelet; 3 and 4. the first and the second glume, respectively; 5 and 5a. the third glume and its palea; 6 and 6a. the fourth glume and its palea; 7. lodicules, anthers and ovary; 8. grain.]