17 
remains as a decapitated disc, serving only as a locus 
of attachment for plants of other genera. In the 
immediate neighbourhood of these relics may be found, 
in all probability, a flourishing crop of young plants—the 
progeny of the destroyed parents. 
Some genera of the Fucaceae show a biennial habit. 
The young plants make vegetative growth during the 
first year and defer the formation of conceptacles until 
the next year. This is the case with Himanthalia lorea. 
In the autumn thousands of minute “ buttons ”’ adorn the 
crevices and irregularities of the rock surface in places 
where this alga grows (Plate I). Side by side with these 
infant plants are other “ buttons,’ one year old and 
already full grown, from whose centres may be seen 
sprouting an inch or two of strap-shaped receptacle. 
Nearby may be found plants of two years’ growth with fully 
developed receptacles bearing a load of epiphytes whose 
increasing weight will eventually accelerate the destruction 
of the Himanthalia host. 
The simultaneous occurrence of Himanthalia buttons of 
all ages indicates that vegetative growth can be carried 
on independent of the march of the seasons. The above 
statement will stand for all algae included in the list of 
perennials. It must not be supposed, however, that 
perennial plants are entirely insensitive to the alternation 
of physical conditions throughout the year. The 
periodicity of seasonal change is reflected in the production 
of reproductive organs at one specific season of the year. 
It is interesting to note that even for allied genera and 
species the same season is not necessarily selected for 
reproduction. The Fucoids, for example, show among 
their genera considerable diversity in their times of 
reproduction. Ascophyllum nodosum reproduces from 
February to May with a high point of fertility in April. 
Fucus vesiculosus follows, beginning in April and rising 
B 
