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.
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.
The inflorescence is an erect, narrow panicle consisting of spikes varying in number from 5 to 12 and in length from 2 to 3 inches. The spikes are erect, pressed to the very slender rachis, longer than the internodes of the main rachis, stalked or sessile, mostly simple but sometimes the lower dividing into two or three branches, 1/2 to 1 inch long. The rachis of the spike is very slender, angular, flexuous, narrower than the spikelets, scaberulous with a few long cilia at the angles.