bursting it, when the upper filaments (pa- 

 raphyses) 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 (^E". Eu- 

 phorbice), the barberry (;E. Berberidis), net- 

 tles (^Z Urticce), Compositae (^E. Composi- 

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

 may frequently be recognized in a dried-up 

 condition, being forerunners of the true spo- 

 riferous bodies (PL 26. fig. 1). The name 

 applied to these organs is spermogonia. The 

 filaments converging into the centre of these, 

 termed sterigmata (PI. 26. figs. 2, 3, s t), are 

 the important parts of the structure ; they 

 terminate in rows of minute bodies of oval 

 form, about 1-6000 of an inch long and 

 1-12000 in diameter (ibid, s p}, which be- 

 come detached and separated, falling loose 

 into the cavity, where, by a continued 

 growth and shedding of similar bodies from 

 the converging filaments, they accumulate to 

 form the granular mass above spoken of as 

 existing in that situation. The number 

 ultimately becomes enormous, and a gela- 

 tinous substance is secreted, glueing them 

 into a mass. When placed in water under 

 the microscope, or when wetted by rain in 

 its natural position, the ripe mass swells and 

 is protruded through the orifice of the sper- 

 mogonium on the surface of the leaf. By a 

 longer action of moisture the jelly dissolves, 

 and the minute bodies {spermatia) spread 

 about in the water, exhibiting "an oscilla- 

 tory motion, as of a body attached at one 

 extremity." De Bary states that he found 

 iodine arrest this motion, while it persisted 

 for some time in solution of chloride of cal- 

 cium. No cilia can be detected. Fresh 

 spermatia were coloured bright purple red 

 by sugar and sulphuric acid, but at the same 

 time were so acted on that it could not be 

 made out whether they possessed a mem- 

 brane free from nitrogenous matter. Solu- 

 tion of potash renders invisible the outlines, 

 not only of the spermatia, but of the sterig- 

 mata and paraphyses. The resemblance of 

 these bodies to the spermatia of the Lichens 

 (see LICHENS), is too evident to be mis- 

 taken ; hence the same terms are applied to 

 the corresponding organs. 



The spermogonia occur either in regular 

 groups, or scattered just like the perithecia j 

 when the latter are on the same surface of 

 a leaf, they often form a circle round the 

 former. Frequently they burst through on 



i ] ^ECIDIUM. 



opposite sides of a leaf j and then the sper- 

 mogonia are oftenest on the upper, the peri- 

 thecia on the lower face (PI. 26. fig. 1 sp). 



After a number of spermogonia have been 

 successively developed and discharged their 

 spermatia, the mycelium, from which they 

 originated, produces a new globular body 

 formed of densely interwoven filaments, 

 usually in the interior of the substance of 

 the leaf or stem, not immediately beneath 

 the epidermis, and ordinarily colourless. 

 Increasing in size in all directions, this glo- 

 bular body, the perithecium, soon presents 

 at its base, i. e. the point furthest from the 

 nearest epidermal surface, another body 

 composed of very numerous free-ending 

 filaments enclosed in a cellular membrane, 

 which body rapidly grows up within the 

 perithecium, in the direction of the surface 

 of the leaf or stem. The filaments, at first 

 very delicate, are crowded very close to- 

 gether ; and each exhibits in its interior a 

 row of short, colourless, roundish cellules, 

 the uppermost of which is always the largest 

 and the most advanced in development. 

 These cellules are the spores, and the fila- 

 ments in which they are found are the spo- 

 rangia or thecce. The membrane enclosing 

 the sporangia, the peridium of Persoon, 

 grows part passu with them, and is com- 

 posed likewise of rows of cells, which stand 

 in a circle around the sporanges, but are 

 firmly connected together side by side by 

 an intercellular substance ; this membrane 

 closes in like a bell or vault over the spo- 

 ranges. By the reciprocal pressure of all 

 parts, the cells of this membrane, at first 

 spherical or ovate, become polygonal. At 

 a certain stage the apex of the perithecium 

 gives way, so that it forms a kind of cup 

 around the membrane enclosing the mass 

 of sporanges arising from the base. The 

 whole structure has by this time come im- 

 mediately up to the underside of the epi- 

 dermis, which is next ruptured, and the pe- 

 rithecium and the sporanges are protruded, 

 more or less, according to the habit of the 

 species (PI. 26. fig. Ip,p). The upper por- 

 tions of the rows of cells composing the pe- 

 ridial membrane then separate more or less 

 from each other, splitting into lobes, so as 

 to set the sporanges free, and form a kind of 

 cup with toothed margins seated in the ex- 

 panded perithecium (figs. 6 and 6 a). 



The spores, which are at first delicate 

 cellules, subsequently acquire a tough mem- 

 brane, increasing considerably in size, so as 

 to distend the parent utricle or sporange, 



