Hickory-nut.—Several species of hickory-tree, all natives of N. America, afford edible nuts. The fruits of the Peccan or Illinois hickory (Carya olivceformis), u common tree on the Ohio and Miasiesippi, are light-brown in colour, and shaped like an olive ; they are much superior in flavour to the nuts of any other species of the genus, and occasionally are found in English fruit-shops. The nuts of the shell-bark hickory (C. alba) are second in point of edible qualities. The nuts of nearly all these trees arc valuable for their oleaginous properties (see Oils—Hickory-nut).
Kola-, or Guru-nut.—This name is applied to the seeds of Cola [Sterculia] acuminata, a tree indigenous to W. and central tropical Africa, and introduced by the negroes into Brazil and the W. Indies. These nuts are held in the highest estimation among the African races, for promoting digestion, and rendering stale water potable ; and they form a most important article of commerce from the Angola to the Mediterranean. Chemical examination of the nuts has proved them to contain an alkaloid, similar to that of tea or coffee, and they are habitually used as substitutes for our ordinary dietetic beverages by foreigners residing in the localities producing them. They are said to promote digestion, support fatigue, and produce a generally bracing effect upon the system. When better known, they will doubtless be cultivated in our tropical colonies, especially as they flourish both on the sea-coast and inland.
Palm-nut.—Tbe well-known palm-oil of commerce (see Oils—Palm) is the product of the outer flesby coating of the seed of Elceis guineensis, a palm indigenous to W. tropical Africa, where it is found in great abundance, and whence it has been introduced into the W. Indies. Some oil is also yielded by the seed. The shell of the nut takes a fine polish, and is made into ornamental articles by the negroes. The geographical range of this palm in Africa extends from the coast of Guinea to the south of Fernando Po, and into the interior as far as Zhern, 400 miles from the sea, and the mouth of the Min, a tributary of the Niger. It flourishes also on the islands of Zanzibar and Pemba ; occurs on the mountains of Usagona; and is plentiful around the lakes of Central Africa. Its limits are probably far from being yet defined. Strangely enough, beyond a successful attempt to introduce this most useful tree into Labuan, virtually nothing has been done to extend its range, and we remain absolutely dependent upon the W. African ports for our supplies of the oil.
The following notes convey all that is known about the cultivation of the palm. The ground is first well-raked, and the ripe nuts selected for sowing are scattered broadcast over the prepared ground, and lightly covered with earth, or 6-10 nuts are dropped together into holes at various distances, and covered with earth. The planting is effected during the rainy aeason, as moisture is essential. When the young shoots aro about 1 ft. high, they are carefully removed in the evening, and transplanted at distances of at least 15 ft. from each other ; the beat plan is to let them remain during 12 months, before performing the transplantation. The tree grows luxuriantly, and bears abundantly when it is 10-12 ft. high, if in a damp, semi-marshy soil, where water does not stagnate ; but in dry, arid soil, it becomes stumpy, growing very slowly, and sometimes bearing fruit when only 4 ft. high. To ensure healthy trees, and a full crop of " fat nuts," the trees must be at least 20 ft. apart, and well supplied with water. The harvest of nuts fit for use is biennial, hut the chief quantity of commercial oil is obtained from nuts gathered during the rainy season. The kernels now form a distinct article of trade, not less important than the oil itself: 27,873 tons were shipped from Lagos in 1878; 100,000 tons from Sierra Leone in 1870 ; 104 tons from the Gambia in 1877, and 87 tons and 91 bags in 1878. The meal left after expressing the oil from these kernels is one of the most valuable fat-producing foods for cattle, its analysis showing:— Moisture, 7'49; fatty matters, 26.57; albuminous compounds, 15 75; starch, mucilage, sugar, and digestible fibre, 37.89 ; woody fibre, 8.40 ; ash, 3.90 per ceut.
Physic-nut.—This name is applied to the seeds of Curcas purgans [Jatropha Curcas], from the powerfully purging qualities of the oil expressed from them. The plant is indigenous to tropical America, and is very generally found in warm climates, being cultivated in Brazil, the E. and W. Indies, W. Africa, the Cape Verde Islands, the Philippines, &c. It is readily increased by cuttings, which rapidly take root, and is invaluable as a hedge-plant, the leaves being refused by all cattle. The Cape Verdes produced 16,672 tons of the seeds in 1869. The wider cultivation of the plant in our tropical colonies would be amply repaid by the oil (see Oils—Pulza).