tECIDIUM. 



[ 14 ] 



iECIDIUM. 



sition of eveiy kind of substance, either 

 natural or artificial, should be known, which 

 would imply an amount of knowledge pos- 

 sessed by no one. But the question is sim- 

 plified in practice, because svibstances used 

 in adulteration must be cheap, and either 

 grown or manufactured in quantities at home, 

 or imported from abroad. Hence they are 

 generally common, and it is pretty well 

 known of what they will probably consist. 

 When the adulteration consists of a chemical 

 substance as it might be called, i. e. a salt, 

 metallic oxide, proximate principle, &c., its 

 nature is readily determined by chemical 

 analysis ; but when it consists of a vegetable 

 tissue, which has been perhaps subject to a 

 partly chemical process of manufacture, the 

 judgment must be based upon the form of 

 the various parts, their size, relative position, 

 and other particulars holding a place in the 

 Table already alluded to. 



BiBL. Ure, Dictionary of Arts and Ma- 

 nufactures; Mitchell, Adulterations of Food; 

 Normandy, Handbook of Commercial Ana- 

 lysis ; Reports from the Select Committees 

 of the House of Commons ; various papers 

 in the last five volumes of the Lancet, and 

 the last two volumes of the Medical Times 

 and Gazette, (the best on record) ; Pereira, 

 Materia Medica; Aikin, Arts and Manu- 

 factures. 



iECIDIUM, Persoon.— A genus of Cseo- 

 macei (Coniomycetous Fungi), consisting of 

 numerous parasitic fungi infesting leaves and 

 herbaceous stems, appearing in their full- 

 grown condition as little cups filled with a 

 reddish or brownish powder (spores), formed 

 by a raising-up and bursting of the epidermis 

 by the parasite developed within. Many may 

 be detected in earlier stages by the deformi- 

 ties they produce in the growing structure 

 of the plants infested, or by pale or reddish 

 spots on the green surface, arising from the 

 presence of the imperfect fungus underneath. 

 These plants are commonly know n under the 

 name of blight, brand, &c. Their history 

 has recently received much elucidation at the 

 hands of Tulasne, De Bary and others, and 

 they are found to exhibit a more complicated 

 organization than was formerly imagined. 

 The organs of fructification are produced in 

 two kinds, bearing great resemblance to the 

 conditions lately ascertained to exist gene- 

 rally in the Lichens. A brief account of the 

 natural history of certain of the species, de- 

 rived from De Bar}^, will give a general idea 

 of the character of this genus. 



The nascent ^cidia are observed as mi- 



nute spots upon the herbaceous parts of the 

 plants which they infest. When sections are 

 made of these and placed under the micro- 

 scope, it is found that the parenchyma of the 

 plant is deformed, irregular, and interrupted 

 by large intercellular passages, among which 

 ramify the filaments of the mycelium of the 

 fungus; these are delicate, much-branched 

 and septate, about 1-3600 of an inch in dia- 

 meter. At certain points these filaments are 

 crowded and interwoven into hollow globular 

 conceptacles, about 1-180 of an inch in dia- 

 meter, immediately beneath the epidermis, 

 the interior of which conceptacle is lined 

 with delicate filaments (about 1-12000 of an 

 inch in diameter) arising at all parts and con- 

 verging toward the centre, except at the 

 upper part, (which is open, and only shut 

 from the external air by the persistent epi- 

 dermis of the 'nurse-plant,') where they are 

 directed upwards. A granular mass occupies 

 the centre of the conceptacle, separating the 

 converging filaments from each other. By 

 the growth of the upper filaments and the in- 

 crease of the central granular mass, the whole 

 structure increases in size, so as to push the 

 epidermis up above the surrounding surface, 

 finally bursting it, when the upper filaments 

 (parajohyses) grow out through the orifice and 

 form a little funnel-shaped tuft on the sum- 

 mit of the protuberance, through the middle 

 of which the granular mass formed below 

 makes its escape. These bodies may be 

 found commonly on the Spurges {^. Eu- 

 jjhorbice), the Berberry {JE. Berberidis), 

 nettles {jE. Urticce), Compositae (^. Compo- 

 sitarum), &c., early in the season ; later, they 

 may frequently be recognized in a dried-up 

 condition, being forerunners of the true spo- 

 riferous bodies (PI. 20. fig, 1). The name 

 applied to these organs is spermagonia. The 

 filaments converging into the centre of this, 

 termed5fen^m«^a(P1.20.figs. 2,3,*^), are the 

 important parts of the structure ; they termi- 

 nate in rows of minute bodies of oval form, 

 about 1-6000 of an inch long and 1-12000 

 in diameter (ibid, sp), which become de- 

 tached and separated, falling loose into the 

 cavity, where, by a continued growth and 

 shedding of similar bodies from the con- 

 verging filaments, they accumulate to form 

 the granular mass above spoken of as exist- 

 ing in that situation. The number ultimately 

 becomes enormous, and a gelatinous sub- 

 stance is secreted, glueing them into a mass. 

 When placed in water under the microscope, 

 or when wetted by rain in its natural po- 

 sition, the ripe mass swells and is protruded 



