I2 
THE. EFFECT OF ALTERNATING SEASORSa 
THE -ALGAL - VEGETAMGl 
To the casual observer the alternation of winter and 
summer brings little apparent change in the character of 
the algal population of the shore. This impression is 
largely due to the fact that the more obvious algae such as 
Fucoids and Laminarians are perennial plants. The 
algologist, nevertheless, is well aware that the number of 
genera and species represented in the flora is less in winter 
than in summer, and many of those species that do occur 
all the year round may be present in smaller numbers and in 
more restricted localities in the colder months of the year. 
Hence there is in reality a distinct fluctuation in richness 
of the flora as the seasons succeed one another, with a well- 
marked crescendo in the early summer accentuated by the 
influx of a large body of what have often been described, 
though sometimes without adequate reason, as “ summer 
annuals.” 
Speaking generally, the poorest season for marine algae 
is in November and December. At this time of the year 
the algal population is at its lowest ebb though this does 
not necessarily imply that all growth and development is 
at a standstill, On the contrary, some of the Rhodo- 
phyceae (species of Polysiphonia, etc.) and certain erratic 
genera (Phyllitis) shew signs of more vigorous growth at 
this period than at any other. The general algal popula- 
tion, nevertheless, is reduced to its lowest terms as a 
consequence of partial depopulation of the shore during 
the autumn—a process brought about either by rough 
weather or by other inclement physical changes in the 
environment. 
In the early spring, signs of general rejuvenation and 
re-colonisation of the littoral zone are observable. From 
February onwards there is a constant stream of new 
