403 



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DICT 



each, a pair of unequal heart-shaped ap- 

 pendages, the stipules. [G. D.] 



DICOTYLEDONOUS. Having two coty- 

 ledons. 



DICOTYLEDONS, DICOTYLEDONE.E. 

 Plants having two seed-leaves or seed- 

 lobes, which are called cotyledons. This 

 is one of the primary divisions or classes 

 of the vegetable kingdom, including about 

 7,000 known genera, and about 70,000 

 known species of flowering plants. The 

 class also receives the name of Exogencc or 

 Exogens, from the structure of the stems. 

 The plants in this great class have spiral 

 vessels ; their stems are formed by addi- 

 tions externally in the form of zones or 

 rings ; stomata or pores exist in the leaves, 

 which have a reticulated or netted vena- 

 tion. The plants have stamens and pistils, 

 either in the same or in different flowers. 

 The symmetry of the flowers is represented 

 by five or two, or multiples of these num- 

 bers. The ovules are contained in an ovary, 

 or more rarely are naked ; and the em- 

 bryo has two, sometimes more, cotyledons. 



In De Candolle's system this class of Dico- 

 tyledons is divided into four sub-classes :— 

 1. Thalami florae, petals distinct; stamens 

 hypogynous ; 2. Calyciflorce, petals distinct 

 or united ; stamens perigynous or epigy- 

 nous ; 3. Corolliflorce, petals united ; sta- 

 mens usually attached to the corolla, which 

 is hypogynous ; 4. Monochlamydece, includ- 

 ing' Gymnospermw, a calyx only, or no 

 floral covering. Lindley divides the class 

 into four subclasses : 1. Diclinous, those 

 plants which have separate staminate and 

 pistillate flowers. Those which have sta- i 

 mens and pistil in every flower are divided 

 into — 2. Hypogynous, stamens not adher- 

 ing either to calyx or corolla; 3. Perigynous, 

 stamens adhering to either calyx or co- 

 rolla ; and 4. Epigynous, stamens, calyx, 

 and corolla, all adhering to the side of the 

 ovary. Gymnogens, or plants with naked 

 seeds, represent a separate class according 

 to Lindley. The age of Dicotyledonous 

 trees can be computed by counting the 

 number of annual concentric rings of 

 wood. [J. H. B.] 



DICR.EA. Herbaceous plants, natives 

 of Madagascar, &c, constituting a genus 

 of Podostemaeew, characterised by herma- 

 phrodite flowers unprotected by a bract ; 

 monadelphous stamens ; and ribbed fruit 

 opening by two equal valves, pi. T. MJ 



DICRANODIUM. Gymnogramma lepto- 

 phylla. 



DICRANOGLOSSUM. A genus of poly- 

 podiaceous ferns of the group Tom'di.da.e, 

 in which the sori are naked, linear, con- 

 tinuous, and submarginal as in Tcenixrpsis; 

 but the veins, instead of being straight 

 and free, or combined by the transverse 

 receptacle, describe a series of simple 

 elongated arcs, each one uniting with 

 the next, and thus forming a continuous 

 irregular curved sub-marginal receptacle ! 

 to which the spore cases are affixed. I). sub- j 

 p-innotifidum, a South American and West 1 



Indian plant, with furcately-lobed fronds, 

 is the only species. [T. MJ 



DICRANOLEPIS. A genus of thymela- 

 ceous plants, the flowers of which have a 

 salver-shaped perianth with a five-parted 

 limb, and ten scales inserted in its throat ; 

 stamens ten, attached to the perianth ; 

 ovary stalked, with a cup-like disk at the 

 base, one-celled, containing a single pen- 

 dulous ovule. There is only one species, D. 

 djstieha, which grows at Sierra Leone: a 

 shrubby plant Avith distichous leaves, and 

 solitary axillary flowers. [J. H. B.] 



DICRANOPTERIS. A synonyme of Glei- 

 clienia ; also applied by some writers to a 

 section of Polypodium. 



DICRANOSTIGMA. A genus of Papa- 

 veracew, represented by a plant indigenous 

 in the Himalayan mountains. It has nume- 

 rous radical pinnately-lobed leaves covered 

 with short hairs ; the stems are about a 

 foot in height, and bear at the top two or 

 three golden-coloured flowers, with a flask- 

 shaped ovary, surmounted by thickened 

 stigmas with two erect awl-shaped arms 

 alternating with the placentas. Its nearest 

 ally is Clielidonium, from which the form 

 of the ovary and stigmas abundantly dis- 

 tinguish it. [M. T. M.] 



DICRANUM. A large and important 

 genus of acrocarpous mosses, distinguish- 

 ed by the unequal cernuous capsule, the 

 hood-like calyptra, rostrate lid, and single 

 peristome consisting of sixteen equidis- 

 tant teeth which are confluent at the base, 

 and split half way down or more into two 

 unequal portions,the medial line being con- 

 tinued to the base, and occasionally perfor- 

 ated. Leucobryum is distinguished by the 

 peculiar structure of the leaves, and their 

 consequent pallid hue. The species, from 

 the different habits which they assume, are 

 distributed into several distinct sections. 

 They grow variously on rocks, or on the 

 ground, or more rarely on the trunks of 

 trees. Some of them, as D. scoparium, are 

 amongst the larger mosses, and remark- 

 able for their long and often curved leaves, 

 while others are minute. It is observed 

 by Wilson, in his Bryologia, that in se- 

 veral of the larger species, which have the 

 stem covered with a dense layer of radical 

 fibres, the male plants appear to be re- 

 placed by minute bulbs, nestling among 

 the fibres ; and this is all that is known of 

 the male inflorescence of certain species; 

 but in D. scoparium the inflorescence may 

 sometimes be traced from these radicular 

 gemma? Up to the perfect development of 

 male plants. A somewhat analogous pro- 

 cess is observable also in a few species of 

 Hypnum. [M. J. B.] 



DICTAME BLANC. (Fr.) Dictamnus di- 

 bits. — DE CRETE. Origanum Dictam- 

 nus. 



DICTAMNCS. A small genus of Buta- 

 ceo3, found in southern Europe, Asia 

 Minor, &c. D. Fraxinella and D. allma are 

 both cultivated in gardens for their fra- 

 grant leaves, as well as for the hand- 



