Strobilus in Archegoniate Plants . 345 
zygote and formation of numerous spores, the way in which 
archegoniate plants evaded the difficulty which their land- 
habit presented to constantly recurrent fertilization ; instead 
of many zygotes leading by direct germination to a supply 
of new individuals, the increase in number of the Archegoniatae 
was brought about by subdivision of the zygote, and formation 
of numerous carpospores. It would further appear that— 
other things being equal— -the larger the output of these 
spores, the better the chance of survival of the species which 
produced them : a comparison of types of the homosporous 
Archegoniatae may illustrate a probable line of increase in 
spore-production : from the simple Riccia , through various 
larger Bryophytic forms, we may rise, with an ever-increasing 
output of spores, to such plants as the Equiseta, Lycopods, 
and Ferns, in which the output of spores was, and is, among 
the largest in the vegetable kingdom. I have calculated that 
a large Male Fern (by no means large among Ferns) may 
produce many millions of spores in each year ; I leave it to 
others to estimate the number of spores produced annually 
by a large Alsophila or Cyathea ; clearly the number is much 
larger than is matured from a single sporogonium of any 
Bryophyte, and it is to be remembered that while sporogonia 
are developed within one season, most homosporous Vascular 
Cryptogams are perennials. 
In the heterosporous forms, however, with the sexual 
differentiation of the spores, there followed a reduction in 
the number of the female spores, counterbalanced by the 
greater certainty of success of the offspring, as following on 
the larger supply of nourishment contained in the enlarged 
female spores. The male spores still continued numerous, 
as in the case of Coniferous pollen ; but finally the amount 
of pollen required to ensure fertilization was economized 
among those higher plants which show perfection in pollinating 
mechanism. Thus we may conclude broadly that the climax 
of numerical spore-production was among the homosporous 
Vascular Cryptogams. 
But such an increased production of spores as we have 
A a % 
