126 



HENDERSON'S HANDBOOK OF PLANTS 



DIG 



several ■weeks. D. muaaica is a beautiful 

 omamental-foliaged species, with dark-green 

 leaves, profusely penciled and veined, with 

 zig-zag lines of pure white ; under side red- 

 dish-purple. Propagated by division in spring, 

 when the new growth commences, and by 

 seeds. 

 Dicho'tomous. Having the divisions always in 

 pairs; a term equally applied to branches, 

 veins, or forks. 



Dickso'nia. Named after James Dickson, a 

 famous British cryptogamio botanist. Nat. 

 Ord. Polypodiace(B. 



A genus of very ornamental Ferns, mostly 

 arborescent, and including some of the most 

 valued Tree Ferns to be found in our green- 

 houses. D. antartica, a native of Australia, 

 introduced in 1824, is the one most commonly 

 grown, and is the most ornamental of the 

 genus. X). arborescens, a native of St. Helena, 

 grows about twelve feet high, bearing at its 

 summit a number of pinnated fronds, from ten 

 to twelve feet in length. This species grows in 

 great abundance in St. Helena, and next to 

 the tomb of Napoleon, is the great attraction 

 of the island. It is remarkable that this 

 species has not been found in any other part 

 of the world. All the Tree Ferns should be 

 grown in a mixture of loam and leaf mould, 

 and require a humid atmosphere. Young 

 plants may be raised from spores, but it takes 

 many years for them to grow to the size of 

 imported stems, to which method we are 

 indebted for all our large plants. One species, 

 X). pvmctilobula, a hardy herbaceous plant, is a 

 native of this country, very common in moist, 

 rather shady places. It is one of our hand- 

 somest Ferns, and has an agreeable odor. 



Dicli'ptera. From dikloa, double-doored, and 

 pteron, a wing ; referring to the two-winged 

 capsule or seed vessel. Nat. Ord. AeantJiacecB. 

 An extensive genus of annuals and peren- 

 nials, allied to Justicia. The species are dis- 

 persed over the tropical and sub-tropical 

 regions of the New and Old World. The 

 annuals grow readily from seed, which should 

 be started in a hot-bed, or the green-house, in 

 March, grown on until all danger from frost 

 is past, and then transplanted In the open 

 border. The perennials are increased by cut- 

 tings. They all require a very light, rich 

 fibrous soU. 



Dicotyle'dons. Plants having two seed leaves, 

 which are called cotyledons. This is one of 

 the primary divisions or classes of the vege- 

 table kingdom, including about 7,000 known 

 genera, and about 70,000 known species of 

 flowering plants. The class also receives the 

 name of Exogens, from the structure of the 

 stems. The plants of this great class have 

 spiral vessels; their stems are formed by 

 additions externally in the form of zones or 

 rings ; stomata or pores exist in the leaves, 

 which have a reticulated or netted venation. 

 The plants have stamens and pistils, either in 

 the same or in different flowers. The sym- 

 metry of the flowers is represented by five or 

 two, or multiples of these numbers. The 

 ovules are contained in an ovary, or more 

 rarely are naked; and the embryo has two, 

 sometimes more, cotyledons. 



Dicta'mnus. Fraxinella, Gas Plant. An ancient 

 name, supposed to have been given because 



DID 



the leaves resemble those of the ash ; hence 

 the English name, Fraxinella. Nat. Ord. 

 RviacecB. 



A small genus of hardy herbaceous peren- 

 nials, and among the oldest inhabitants of the 

 cottage garden. Johnson says: "Instances 

 are known where D. Framnella has outlived 

 father, son, and grandson in the same spot 

 without increase, all attempts at multiply- 

 ing it, to give away a rooted slip to a newly- 

 married member of the family, having failed ; 

 yet the Fraxinella is easily increased from 

 seeds, which should be sown soon as ripe in 

 any common garden soU. They will come up 

 the following spring." The plant has to be 

 three years old before it will flower. It is a 

 native of Germany. When rubbed the leaves 

 emit a fine odor, like that of lemon peel ; it is 

 strongest in the pedicels of the fiowers. The 

 whole plant emits a resinous or oily matter, 

 which may be readily ignited, especially in 

 warm weather. 



Dictya'nthus. From diktyon, net work, and 

 cmthoB, a flower; the flowers are netted with 

 veins. Nat. Ord. Asclepiadouxoe. 



Green-house climbers of considerable 

 beauty, from Central America and Brazil. 

 They wiU do well, planted out in summer, but 

 require gr^en-house culture during winter. 

 The same treatment that is given the Passi- 

 flora will suit them. The flowers are whitish- 

 purple and greenish-brown, borne on axillary 

 peduncles. D. campounulalua somewhat re- 

 sembles the Stapelia. Propagated by cuttings. 

 Introduced in 1851. 



Dictyogra'mma. A genus of Ferns now 

 placed under Gymnogranvma. 



Dietyo'pteris. From diktyon, a net, and pteria, 

 a Fern; referring to the fronds. Nat. Ord. 

 PolypodiacecB. 



A genus of Ferns from Australia, without 

 special merit, and rarely met in collections : 

 now placed under Polypodium. 



Dictyospe'rma. From diktyon, a net, and 



sperma, a seed ; in allusion to the raphe of 



the seed forming a loose net- work. Nat. Ord. 



PaVmoAxcR. 



A genus of warm-house Palms, closely al- 



. lied to Areca, from which genus it is botanically 

 distinct. 



Didi'sous. Derivation of name not given. Nat. 

 Ord. Umbelliferm. 



The two species that compose this genua 

 were formerly included in Trachymene. D. 

 caeruUus is a showy plant, a native of Austra- 

 lia. It is covered with hairs ; its leaves are 

 three-parted, each division again sub- 

 divided; its flowers are blue. The fruit, 

 when mature, is covered with small tubercles. 

 D. albiflorua has no hairs, and its flowers are 

 white. 



Did3rmooa'rpus. From didymoa, twin, and 

 kairpos, a fruit ; in reference to the twin cap- 

 sules. Nat. Ord. Oesneracece. 



A genus of upwards of thirty species of 

 caulescent or stemless herbs, or under- 

 shrubs, natives of tropical Asia. The 

 flowers are violet-blue, rarely yellow, leaves 

 usually cordate, wrinkled, and hairy. Those 

 in cultivation are neat, pretty plants ; propa,- 

 gated by cuttings of the young wood. 



