276 



DICHELESTIUM DIDELP II US. 



Linnaeus, Lilt since new named as above. They are 

 easy of management and propagation, like other stove 

 plants. 



DICHELESTIUM (Hermann). A curious 

 genus of parasitic, entomostracous, crustaceous ani- 

 mals, belonging to the order PaEcihpoda, and section 

 Siphonostoma, having the body long and narrow, com- 

 posed of seven segments, the first of which is larger 

 than the rest, with a pair of slender filiform antenna;, 

 a pair of short didactyle claws, a tubular sucker, three 

 kinds of feelers, four short legs for prehension, termi- 

 nated by several toothed hooks ; the second and third 

 segments are lunate in form and furnished with very 

 short legs ; the sixth segment is long and somewhat 

 cylindric, and the last small and oval. The animal 

 of which this genus is composed is rather more than 

 half an inch long, and insinuates itself into the flesh 

 and the gills of the sturgeon, as many as a dozen 

 having been found upon one fish. Of this number 

 three of the specimens were one-third smaller than the 

 others, with the body curved : one of them lived three 

 days when removed from the fish. They are enabled 

 to retain firm hold of their prey by means of their 

 strong frontal pincers. 



DICHLAMYDE^E, a subdivision of dicotyledo- 

 nous plants, including those which have a double 

 floral covering, or both a calyx and corolla. The 

 greater part of the handsome flowering trees and 

 shrubs are found in this division. 



DICHONDRA (Forster). A genus of evergreen 

 creepers, natives of the West Indies. Linnsean class 

 and order, Pentandria Digynia, and natural order 

 Convolvulaceiz. This succeeds well with ordinary 

 stove management, and may be increased by cuttings. 



DICKSONIA (Heretier). A genus of exotic 

 ferns, so named in honour of James Dickson, a British 

 cryptogamist of great abilities and unwearied indus- 

 try. It belongs to the order FiKces, and one of the 

 species is a tree fern from St. Helena. 



DICLIPTERA (Vahl). A genus of tropical 

 plants, mostly under shrubs, belonging to the class 

 Diandria, and to the natural order Acanthacece. Gene- 

 ric character : calyx bracteate in four or five divisions ; 

 corolla two-lipped, the lowest nearly entire ; anthers 

 two-celled ; capsule roundish, nearly one-celled, dis- 

 sepiment ultimately free, to whicn the seeds are 

 attached. This genus is nearly allied to Justicia, but 

 differs in the structure of the capsule. It thrives in 

 rich light soil, and is propagated by cuttings. 



DICLYTRA (Borckhausen). A diadelphous 

 genus of plants found in the north of Asia and 

 America, and belonging to the natural order Fuma- 

 riaceas. Some of the species were at first called 

 Fumaria, and others Corydalis ; but these, together 

 with five others, are now known by the name first 

 above given. 



DICOTYLEDONES, or EXOGEN^E, a divi- 

 sion of vascular, flowering, or phaenogamic plants, in 

 which the vessels are arranged in concentric layers, 

 the youngest of which are external, and the cotyle- 

 dons of the embryo are opposite or verticillate : the 

 dicotyledonous plants have a more or less conical 

 trunk, consisting of bark, wood, and pith ; the wood 

 being contained between the other two. The thick- 

 ness of the trunk is increased by an addition of new 

 matter between the wood and bark. They have 

 reticulated leaves which are distinctly articulated with 

 the stem. The veins of the leaves are much branched ; 

 the flowers have generally a double perianth (dichla- 



mvdeous), and frequently exhibit a quinary divisiua 

 The embryo is furnished with two cotyledons (hence 

 the term dicotyledonous), which after germination, 

 frequently assume the appearance of leaves. By 

 these characters the plants of this division are distin- 

 guished from those of the monocotyledonous class. 



DICTAMNUS (Linnaeus). Hardy ornamental 

 herbaceous plants, said to be natives of Crete, but 

 long cultivated in this country under the name of 

 Fraxinella. The flowers are decandrious, and accord 

 in character with those of the natural order Rutaccce. 

 There are two species, both of which grow any where, 

 and are raised from seeds. Dictamnus is also a specific 

 name of an origanum (marjoram), commonly called 

 Dittany of Crete. 



DICTYOPTERA (Leach). The family of the 

 cock-roaches (Blattidee], on account of the flattened 

 oval form of the body, the five-jointed tarsi, and several 

 other less important characters, was considered by 

 Dr. Leach as sufficiently distinguished from the other 

 orthopterous insects to warrant its separation as a 

 distinct order, to which he applied this name. His 

 arrangement has not, however, been followed in this 

 respect. See BLATTA. 



DIDELPHUS Opossum. A genus of marsupial, 

 or pouched animals, inhabiting the American conti- 

 nent, and the first animals of this singular order which 

 are known to naturalists. Their generic characters 

 are ten incisive teeth in the upper jaw, and eight in 

 the under, the intermediate ones in the upper jaw 

 being longer than the rest ; the three front grinders 

 compressed, and the last four tuberculated ; those 

 above triangular, but the under ones oblong, and two 

 canines in each jaw, making in all fifty teeth, which is 

 a greater number than is possessed by quadrupeds 

 of any other genus. Their gape is wide, and the 

 appearance of the mouth ragged ; but their bite is 

 feeble, compared with the size of their biting appa- 

 ratus. Their tongues are beset with horny tubercles, 

 like those on the tongue of a cat ; and their tail is in 

 part naked on the under side, and prehensile. Their 

 ears are large and naked, and their aspect is alto- 

 gether very peculiar. Their hind feet have the thumb 

 or fifth toe long, and capable of acting in opposition 

 to the other four, so as to lay hold like a hand. The 

 four toes which act together on the hind feet are fur- 

 nished with nails ; and when not used in grasping, 

 the nailless one is turned to the rear, like the hind 

 toe of a bird. Their legs are short in proportion to 

 the size of their bodies ; they plant their feet upon 

 the round pad of the sole when they walk, and their 

 rate of motion on the ground is but slow. In trees, 

 however, which the greater number of them chiefly 

 inhabit, they have much power of themselves, and 

 climb and hold on with much address. Their eyes 

 have the irides yellow, and the pupils are vertical, 

 like those of the fox. It has been said of them that 

 they have a gape like a pike, the ears of a bat, the 

 feet of an ape, and the tail of a serpent ; and, cer- 

 tainly, taking their characters all in all, they differ 

 very much from the placental mammalia. The diffe- 

 rence extends not only to the form of the body, and 

 the structure of those parts upon which the classifi- 

 cation is founded, but it extends to the very covering, 

 the hair of the opossum being unlike that of most 

 other animals. It is neither sleek nor frizzled ; and it 

 has more resemblance to whalebone than to common 

 hair, and on the naked parts there are sometimes 

 scales. This uncouth sort of covering the seini- 



