Structure of Grass Spikelets

  Many specific grass names are based on the spikelet structure, which in the past has been the subject of much debate. For example, it has been interpreted both as a flower and part of the inflorescence. As a consequence, specific epithets based on descriptive terms do not necessarily have equivalent meanings. Presently there is little disagreement as to the structure of the spikelet (Clifford 1987).

  In its most generalized form the spikelet consists of several alternating bracts, all but the lower two of which bear short shoots, each of which has a prophyll (palea) beyond which are 2 or 3 scales (lodicules) and then the anthers and pistil. The bracts, also known as glumes, are then divided into sterile or fertile depending upon whether or not they support short shoots. Furthermore, the sterile glumes are referred to as subtending glumes, if they are at the base of the spikelet and the fertile glumes as lemmas. A lemma together with its attendant palea, lodicules and reproductive structures is known as a floret. The flower is generally taken to be the reproductive structures along with the lodicules.

  In earlier times the spikelet was sometimes regarded as a flower, as attested to by the name Monanthochloë whose inflorescences consist of a single spikelet. However each of the spikelets has several florets and accordingly several flowers and so the name is misleading unless interpreted in an historical context. As their role changed from words in every day use to technical terms many Latin and Greek words also changed their meanings and over time many of these have become quite different from the originals. A few of the changes especially relevant to grass morphology are given in Table 1.1.

  Changes, such as those given above, in the meaning of Classical words on their adoption as descriptive botanical terms, should not be confused with the transfer of meaning that resulted from the application to plants of terminology originally applicable to animals.

  Earlier plant anatomical studies were undertaken mainly by human anatomists who gave terms such as ovary to seed bearing structures and cotyledon to the first pair of leaves on the embryonic seedling. Such terminology implied, intentionally or otherwise, a parallelism in function of the structures in plants and animals.