Guilielma
(named in honour of Queen Frederica Guilielma [Wilhelmine] Carolina of Bavaria). ORD. Palmae. A genus (included, by Bentham and Hooker, under Bactris) containing three species of elegant stove palms, confined to the tropical regions of South America. Flower-spike branched. Fruit ovate, about the size of a peach, produced in large pendulous bunches. Leaves pinnate, hairy; leaflets and footstalks spiny. Trunk slender, marked with circular scars, and armed with exceedingly sharp spines. For culture, see Bactris. G. speciosa (showy).* l. 2ft. to 4ft. long, pinnate; pinnae about 1ft. long, 1in. wide, apex broader, bifid, deep green nerves on the upper sides clothed with slender black bristles; petioles broadly sheathing at the base, thickly armed with slender long black sharp spines. Stem tall, densely spiny, slender. Amazon. SYN. Bactris Gasipaes.
G. utilis (useful). fl. monoecious. Seeds edible, having the flavour of chestnuts. l., young ones broad and bifid, bristling with short spines, which spring from the ribs or veins, the ridges of the upper surface and the costa beneath being the parts furnished with them; mature ones forming a handsome pinnate head; petioles densely spiny. Trunk slender, spiny. Costa Rica, 1873. (G. C. 1873, 1271.) GUMMOSIS, or GUMMING. Recent observations on this highly contagious disease have shown that it is caused by a fungus, which has been named by Professor Oudemans Coryneum Beijerinckii. The mycelium of this fungus appears to develop a ferment which penetrates the adjacent cells and transforms the cell - walls, the starch granules, and other cell contents into gum, whether these cells belong to the host plant or to the fungus. The ferment of the Coryneum can penetrate into living cells-e.g., those of cambium-and can modify their protoplasm so that the cells that they afterwards produce by division form a tissue with new properties. This tissue is the pathological wood parenchyma. Sooner or later, this tissue begins, in turn, to secrete the ferment, and to change into gum. The quantity of ferment so formed is greater than the amount originally present in the diseased cells. Gumming can be propagated from diseased to healthy places without mycelium extending from one to the other. The action resembles the propagation that albinotic parts exercise on healthy ones. It is conjectured that the channel of propagation is the phloem, and that the contagion is the ferment. In other cases, the mycelium of the Coryneum is the exciting cause of Gumming. A similar disease produces gum arabic, gum tragacanth, and, probably, many resins and gum resins, "One point concerning the spread of this disease seems clear-the fungus itself cannot penetrate the bark: there must be some abrasion or laceration of the latter before the germ tubes can enter. These injuries may clearly arise from many causes; but how do the spores which are undeveloped in the viscid gum gain access to them? That they cannot be blown there by the wind, is obvious. If the Gumming occurs upon the upper branches, of course they may be washed down by the rain; but how do they spread from tree to tree? Obviously, they must be carried-most probably by insects" (Plowright). The best remedy against this disease would, therefore, appear to be the destruction, by burning, of the infested parts, and carefully coating the cut surfaces with some preservative solution. A resume of Dr. Beijerinck's observation and experiments is given in the "Gardeners' Chronicle," n. s., xxii., pp. 239, 410. Fruit-trees affected by Gumming are: Cherries, Peaches, and Plums. Its effects on Peach-trees are most to be dreaded, neither of the others being so much injured as these. In slight cases, the bark should be frequently well washed in damp weather, with a brush and water; but, where the disease pervades the tree to a considerable extent, it is difficult to effect a cure. Gumming occurs most frequently, and is greatly encouraged, where the soil has been too richly manured, and growth is consequently over-luxuriant. The necessity of removing large branches at pruning time should also be specially avoided by judicious summer stopping of the young shoots, in order to divide the sap, and insure an equal medium growth throughout. Lifting and root-pruning, or planting in a poorer soil, might be adopted to check Gumming, where an undue growth is encouraging it.