374 
Notes. 
generations, as we have in these and some other Algae, in the Mosses, 
Ferns and Flowering-plants, fundamentally consists ; namely in the 
production from the fertilized ovum not only of a single new 
individual, but of many. It is in a word polyembryony. Its object is 
the production and dissemination of the greatest number of individuals, 
just following the sexual process, endowed with the maximum of energy. 
Passing up from the Algae which live in water to the lowest of the 
Mosses, Riccia, living on land or floating on the surface of water, the 
sporophore no longer consists merely of a mass of cells each of 
which becomes a spore, but the outer layer of cells give up their 
reproductive function to form a protective covering for the reproduc- 
tive cells and to assist in the distribution of the spores. 
In the Algae the development of a spore- case was unnecessary, 
since the spores immediately on being formed were set free in the 
water, and by means of their vibratile cilia and the currents of the 
water easily distributed at once. 
It is from the simple spore-case of Riccia , and by a further steriliza- 
tion of the sporogenous tissue, that all the complex tissues of the 
sporophore of the higher Liverworts and Mosses, Ferns and Flowering- 
plants, must have been evolved. 
Before proceeding further I must justify the omission of certain 
comparisons in what has gone before. 
The Fungi in which there is alternation of generations have been 
omitted from the review given above, and for the following reasons. 
The alternation of generations, as it is here understood in the 
green plants, begins with Pandorina at the earliest. The great 
phylum of the Fungi is, I think, universally considered to have 
separated from the green plants from a point far below Pandorina or 
any of the Volvocineae, so that alternation of generations in them 
must have originated independently. In certain cases in the Fungi 
alternation of generations appears to have arisen in the way that 
Pringsheim supposed that it had done generally, for instance in 
Phycomyces nitens. Whether alternation of generations in the Fungi 
generally arose by a differentiation from individuals reproducing both 
sexually and asexually, or from polyembryony, I must leave to be 
decided by those better acquainted with the Fungi than I am. 
No comparisons have been made with the Melanophyceae, since, 
as far as we know at present, in that group there is no alternation of 
generations at all. and they remain as a separate phylum. 
