THALLOPHYTES. 
the spermogonia, are disseminated over the surface of the thallus by the agency of water, 
and are thus brought into contact with the projecting cell of each trichogyne, and to this 
they adhere. The contents of one at least of the spermatia pass into the trichogyne in 
consequence of the absorption of the cell-walls at the point of contact, and thus the 
carpogonium is fertilised. It will be seen that this mode of fertilisation is the same as 
that which has been described in the case of the Florideae. In consequence of fertilisa- 
tion the cells of the ascogonium, as well as those of the adjacent hyphae, are stimulated 
to growth, and the result is the formation of an apothecium ; from the ascogonium are 
produced the asci, and from the adjacent hyphge the paraphyses and the wall. It is clearly 
shown that the apothecium is derived solely from the fungal constituent of the Lichen. 
These results, besides throwing light upon the nature of Lichens, give a clue to the 
significance of the spermogonia and spermatia in other Ascomycetes and in the ^cidio- 
mycetes.] 
B. The ^cidiomycetes ^ 
[UredinecE.) 
If, in characterising this group, attention is confined, as in the case of the 
preceding groups, to those forms whose development is completely known, two 
extreme cases, as regard the conditions of reproduction and the alternation of 
generations, present themselves. In the simplest case the mycelium produces 
a fructification, the so-called ^-Ecidium, which consists, in its mature condition, of 
a cup-shaped investment {peridiuni) and of a hymenium occupying its basal part ; 
from the basidia of the hymenium spores are formed by abstriction. The spores 
thus produced {cEcidiospores) at once germinate, and each one developes a short fila- 
ment consisting of but few segments, the growth of which soon ceases, and bearing 
upon short delicate branches smaller reproductive cells, the sporidia, which may be 
included under the term conidia in the sense in which that term has hitherto been 
used. The hypha bearing them is to be regarded as a promycelium. The sporidia, 
on germination, throw out hyphae which penetrate into the epidermal cells of the 
host, and give rise to a mycelium which, in its turn, forms aecidium-fruits. In this 
case, which is found represented by Endophyllum Sempervivi, there occurs a simple 
alternation of generations, the alternating generations being the mycehum and the 
fructification (secidium), with the slight variation that the aecidiospores give rise to 
the mycelium not directly but indirectly by means of the promycehum and its 
sporidia. The other extreme case is represented by jEcidium Berberidts, Vadium 
Leguminosarum, and others. Here new mycelia are directly formed by the secidio- 
spores, without the intercalation of a promycelium. They do not, however, give rise 
to secidium-fruits but develope conidia (the so-called Uredospores) upon basidia closely 
packed so as to form a kind of cushion, by means of which numerous generations 
of myceha are produced during the period of vegetation. It is not until later that 
reproductive cells of another kind, the Teleutospores, are produced in these genera- 
tions to which the name Uredo has been given. These germinate in the following 
^ Tulasne, Ann. des Sei. Nat. 3rd ser. vol. VII; 4th ser. vol. II. — De Bary, Ann. des 
Sei. Nat. 4th ser. vol. XX, and Monatsber. d. Berl. Acad. 1865. — Oersted, Bot. Zeit. 1865, p. 291.— 
Reess, Die Rostpilzformen der deutschen Coniferen, Halle 1869 (Abh. der naturf. Gesellsch. Bd, XI). 
— Oersted's Systena der Pilze, Lichenen, und Algen, translated into German by Grisebach and Reinke, 
Leipzig 1873, p. 19. [Schröter, Entwick. einig. Rostpilze, in Cohn's Beiträge, I, 1875.] 
