340 PRACTICAL COURSE IN BOTANY 
bears the gametes, or sexual organs, — the suffix phyte mean- 
ing a plant ; for example, epiphyte, on or upon plants ; spermo- 
phyte, or spermatophyte, seed plant; sporophyte, spore plant. 
The sporophyte, produced within the archegonium, bears 
simple nonsexual spores that are capable of germinating 
independently. Structurally it is a separate, individual 
organism, though it does not appear as such in this class, 
but lives inclosed in the archegonium, as a parasite on the 
mother plant. 
395. Alternation of generations. — If we represent the 
sporophyte by S, the thallus, or gametophyte, by G, the 
female gamete, or egg cell, by fg, the antherozoids (male 
gametes) by mg, the fertilized egg cell, or odspore, result- 
ing from their union by ods, and the asexual spores dis- 
charged from the sporophyte by 0, this complicated mode 
of reproduction may be expressed diagrammatically as 
follows :— 
fg : fg 
a tiie» S—-o ec pe 00s > S —> 0 —>Gete. 
mug: mg 
A glance at the diagram will show a continual inter- 
change of the sexual and asexual modes of reproduction, in 
which each generation gives rise to its opposite, the asexual 
sporophyte producing the sexual gametophyte, and this in 
turn, through its gametes, giving rise to the asexual sporo- 
phyte. This regular recurrence in genealogical succession of 
two differing forms is what is meant by the expression “ alter- 
nation of generations.” Analogous processes occur also 
among some of the thallophytes, but as there is no well- 
defined differentiation of sporophyte and gametophyte, 
alternation proper may be regarded as beginning with the 
bryophytes. The subject is a complicated one and some- 
what difficult to grasp, but it is important to form a correct 
idea of it and to fix clearly in mind the different modes of 
reproduction as we proceed from the lower to the higher forms 
of vegetation, smce in this way alone can their biological 
