AN ANATOMICAL STUDY OF TRAUMATIC AND OTHER ABNORMAL TISSUES IN CARNEGIEA GIGANTEA

Abstract

Traumatic tissues in Carnegiea giga:ntea are formed apparently in response to acute wounds made by the plant's natural eifemies, birds and insects, and to general surface irritation or weathering. The two types are the same in color, a brownish-gray, and in general texture, though the former is more horny and the latter more bark-like and scaly in appearance. The first purpose of this investigation was to make an anatomical analysis and comparison of the two types. Later, other abnormal vascular structures were studied. There is very little literature on the anatomy of the Cactaceae, and nothing was found concerning traumatic tissue in Canegiea gigantea, although the plant, according to MacDougal (I905), was first mentioned as early as I604. Ganong (I895) merely makes the general statement that perfect occurs in cacti. Schleiden (I839), whose detailed anatomical study of a number of genera of this family is unique, describes and illustrates cork formation in Opuntia and Echinocactus, remarking that this cork is made up of lamellae due to the alternation of layers of thickand thin-walled He agrees with those whom he calls the older anatomists that the bark (by which he declares they usually mean cork ) is an epidermis, and goes on to say that the tissue around wounds and the cork (referring to the bark-like type) are identical. His final conclusion is that all cork is a form of traumatic tissue. Scott (I932), in her study of Fouquicria, which is somewhat close to the Cactaceae, states that the cork cambium produces unthickened cork cells and thick-walled fibrous cork cells. In reference to the fibrous cork, she says, As is seen: from micro-chemical tests only the middle lamella is suberized, and the wall thickening is due to a heavy lining of cellulose. The extreme hardness of this fibrous seemed to indicate that lignin must be present, and made it seem necessary to check her last statement carefuly. It was found that in a phloroglucinol-hydrochloric-acid test, if left for at least twenty minutes, the heavy lining of cellulose becomes a pale violet-red, giving a reaction about one-third as intense as that of ordinary lignified tissue, and showing the presence of some lignin.