homologous Alternation of Generations in Plants. 367 
nation the term ‘alternation of generations’ was first 
applied in animals : it is found in the Thallophytes, 
and might be described as a mere differentiation — often 
a very slight one- — of successive gametophytes. 
Thus, where an antithetic alternation occurs (though 
not in all plants which show sexuality), there are two points 
in the life-cycle, which we may regard as fixed, and com- 
parable in different plants, viz. the zygote , and the carpo - 
spoi'e : the generation which intervenes (e. g. in the Fern 
or Moss) between the zygote and the carpospore, will 
collectively fall under the term sporophyte ; that between the 
carpospore and zygote is termed the gametophyte . Now 
the sporophyte may, in those organisms where it is of con- 
siderable size, reproduce itself in a vegetative manner by 
gemmae or buds (e. g. Lycopods, various Ferns and Phanero- 
gams) : to these modes of propagation the term sporophytic 
budding may be applied, and they may be represented graphi- 
cally as an eddy in the main cycle of life, being mere vegetative 
amplifications. Such means of propagation naturally do not 
exist among the lower forms, where the sporophyte is absent 
or very rudimentary ; but in these the gametophyte may 
multiply by the formation of gemmae of various kinds — e. g. 
Liverworts and Mosses (gemmae), Florideae (tetraspores), 
various Fungi (conidia), and Algae (brood cells), &c. — all 
these are mere vegetative propagations of the gametophyte, 
and may be ranged together under the heading of gameto - 
phytic budding', they are doubtless of independent origin, but 
in their results they are practically identical. In special cases 
more than a single form of gametophytic budding may take 
place in a single family or organism : thus, in the Mosses, a 
formation of gemmae may take place on the protonema, 
and other gemmae be formed on the Moss plant ; again, in the 
Uredineae, various types of conidial reproduction are known, 
which are yet none the less mere repeated gametophytic 
buddings. 
Besides these processes by which amplifications of the life- 
cycle appear, certain stages may be eliminated by apogamy 
B b 
