INTRODUCTION. 
^33 
sporangia of ^Ferns and capsules of Mosses. These are obviously the result of a 
vegetative process, excited by the act of sexual union, in consequence of which 
they arise on the second (non-sexual) generation [sporophore] which springs from 
the fertilised oosphere of the first (sexual) generation [oophore]. Let us now 
transfer these conceptions to the most highly developed Thallophytes which ex- 
hibit an evident alternation of generations, as the Ascomycetes. We have already 
seen, in the Section referred to, that the ascospores of Penicillium are the result 
of a vegetative process brought into action by the sexual organs of the mycelium, 
and which has for its result the formation of the tuberous fructification which 
constitutes the second generation. The ascospores of Penicillium therefore cor- 
respond to the spores of a Moss or a Fern. If now we suppose the result of 
the union of the sexual organs to be a very inconsiderable vegetative structure, 
and the second generation consequently to be merely rudimentary and a simple 
appendage to the first, the spores themselves would then seem to be an almost 
immediate result of fertihsation, as occurs for instance in the Nemalieae (Fig. 164, 
C, p. 237). If we were further to imagine that the act of fertilisation did not 
result in the production of any vegetative structure, or the second generation to 
be altogether suppressed, the fertilised oosphere would then itself become a spore, 
as in the Coleochaetese, (Edogonieae, and Vaucheria. In this case the spore is 
an equivalent for the whole of the second generation ; it stands for the entire 
fructification of the Ascomycetes, the entire spore-capsule of a Moss, &c. Precisely 
the same is true for the zygospore which results from conjugation. The zygospore 
(as for example in the Mucorini), or the oospore (as in Vaucheria), represents there- 
fore in a morphological sense the entire second generation of these plants. This 
conclusion, which might easily be proved more in detail, may be briefly summed up 
in the statement that the Spore is either an immediate product of fertilisation 
(zygospore, oospore), or of a process of growth which is induced by fertilisation ; and 
this vegetative growth may either be inconsiderable, as in the Nemalieae and Erysiphese, 
or it may be considerable, and it then gives rise to the second generation in which 
the spores are produced, as in Penicillium and other Ascomycetes. This explanation 
shows at once how in Thallophytes the second generation is a gradually increasing 
structure developed in consequence cf the act of fertihsation. But for the purpose 
of a scientific nomenclature the term^ Spore (if used in the same sense as in 
Muscineae and Vascular Cryptogams) must be applied in Thallophytes only to 
those reproductive cells which are the result of an act of impregnation, whether 
direct, or indirect through the production of a vegetative body which constitutes 
a second generation and closes the entire course of development of the plant. All 
other unicellular and non-sexual organs of reproduction we shall not term spores, 
but gonidia or conidia. 
We may now proceed to a further description of the various kinds of sexual 
organs found among Thallophytes, and of the true spores which result from their 
union with or without an alternation of generations. The following three principal 
forms or types may be distinguished ^ 
^ More minute evidence of the statements here made will be found in the sequel in the 
description'^of Algce and Fungi. The facts stated are derived from the u^ritings of Pringsheira, 
