SECTION K.—BOTANY. 
THE PHAZOPHYCEZ AND THEIR 
PROBLEMS. 
ADDRESS BY 
Proressor J. LLOYD WILLIAMS, D.Sc., 
PRESIDENT OF THE SECTION. 
WuEN the Botanical Section of the British Association did me the honour 
of inviting me to preside at its meeting, several members of the Committee 
seem to have regarded it as a foregone conclusion that the subject of this 
address would be the Pheophycee. But for this unconscious com- 
pulsion on their part, one would probably have selected some other subject ; 
for the greater one’s interest may be in any department of a science the 
more keenly one realises the difficulties of its problems, and the more 
conscious one is of his own ignorance and helplessness regarding them. 
There are, however, several good reasons for selecting the Pheophyceze 
for discussion at the present time. The study of many life processes 
ought to prove easier and more fruitful when carried on in the simpler 
Alge than in the more complex higher plants; for not only does one 
come nearer to the problems of life and its past history in the Algal world, 
but one is able also to concentrate attention on fewer factors at a time, 
and thus obtain results with far greater expedition and certainty. 
The Pheophycee present a remarkably wide range of plant forms. 
In regard to external form and tissue structure, the higher members of 
the class are the most highly differentiated among the Thallophyta, while 
in size they far exceed any members of the Green or Red Alge. The 
mode of sexual reproduction ranges from isogamy to pronounced oogamy ; 
and, although fertilisation is invariably external, the difference in the 
reproductive schemes and life histories of such representatives as the 
Cutleriaceze, the Dictyotacee, the Laminariaceze, and the Fucacee are 
so great that it is at first difficult to believe in their descent from a common 
stock. And yet the uniformity of structure of the motile reproductive 
cells, with their characteristic lateral cilia, together with the similarity of 
the colouring matter, and the products of assimilation throughout the 
group, are such that there is general agreement as to their close relation- 
ship in the distant past. 
Some recent discoveries in the Pheophycex have added to the interest 
already felt in the group. While previous researches in the Cutleriacew, 
Dictyotacex, and Fucacee had given us the key to the cytological 
relations of their sporophytes and gametophytes, the position of the 
Laminarians was still a paradoxical one, for here we had plants of very 
advanced somatic structure, possessing sieve-tubes comparable with those 
of the Flowering Plants, and yet presenting the most elementary mode of 
reproduction—an asexual one, by means of zoospores. The successful 
ee a 
