1g 
parts indicates that for many genera there is nothing 
inhibitive to growth in the conditions governing any 
season of the year. But new growths require a certain 
time to attain maturity, hence there is observable a seasonal 
fluctuation in mass, attributable not to any direct effect 
of the environment on growth, but indirectly to the 
precipitation of reproduction on a large scale at one 
specific season of the year. | 
All that has been said above about large algae such as 
Fucoids and Laminarians applies equally well to a host 
of smaller genera. Such plants as Laurencia hybrida, 
L. pinnatifida, and species of Chondrus, Gelidium, Gigartina 
and Rhodymenia have a wide range of distribution on the 
shore and come under the category of ‘‘ common ”’ algae. 
In the autumn these plants are considerably depleted in 
numbers or suffer decapitation and are represented in 
the early winter months by their basal parts only, some- 
times reduced to a small disc less than a third of an inch in 
diameter. This relic is firmly adherent to the substratum 
and is capable of sprouting vigorously into new shoots in 
early spring. An illustration may be drawn from the 
behaviour of Laurencia hybrida on limpet shells in pools on 
the limestone terraces at Port St. Mary. In the autumn, 
this area is subject to a considerable amount of scour, 
when many of the Laurencia fronds are removed. In 
January an examination of the limpet shells in this area 
revealed the presence of numerous bases of Laurencia 
plants hidden amongst a covering of Sphacelaria cirrhosa 
(short, tufted, winterform). In February these basal discs 
had already begun to proliferate from the margins and 
showed a new growth of fronds nearly an inch long and 
already bearing antheridia. 
lf definition of the term perennial implies merely 
a capacity for withstanding an unfavourable season, 
then these Laurvencia plants are perennial. This, however, 
: 
