20 
is not quite the end of the matter. It is not known, for 
example, what proportion of the plants remain as persistent 
bases; nor how many times this regenerative process 
may take place in the life of one individual. Young 
sporelings are constantly developing alongside their 
mature relatives and are ready to fill in the gaps. It is 
difficult therefore to estimate with precision the length 
of life of one plant. 
Moreover, the matter is somewhat complicated by the 
fact that many genera show not one but two periods 
a year when new thalli arise; one in the early spring 
and a second in the autumn. The spring plants reach 
a reproductive stage in the early summer and may then 
become submerged under a profuse development of other 
genera. They persist as somewhat debilitated plants 
for a time and then die off or remain only as basal attach- 
ment organs. Meanwhile the autumn crop of vigorously 
growing plants—probably the progeny of the spring 
crop—becomes conspicuous in September and October. 
Some may reach a reproductive stage but the plants 
developing late in the season may fail to do so, and 
remain in a vegetative condition over the winter. The 
renewal of activity of these plants and the development of 
sporelings are together responsible for the next spring crop. 
PSEUDO-PERENNIALS 
It is somewhat difficult to draw a distinction between 
this class and the preceding one, for if the proportion of 
persistent bases falls to a low figure, continuity of the 
species in the flora is maintained largely by the upgrowth 
of young sporelings and the plants cannot be classed as 
perennials: neither are they truly annuals but for con- 
venience have been called “‘ pseudo-perennials.’’ Under 
this heading have been included a number of species with 
a peculiar behaviour. The power of regeneration of 
