Notes on Floriclese. By George Massee. 571 



second type of reproduction which manifested itself in some of the 

 species of the same primitive family of plants, by which, after a 

 limited period of existence as an individual, the sum total of forces 

 constituting its life became concentrated in a small portion possess- 

 ing the power of reproducing its like, the greater bulk of the 

 individual dying, becoming reduced to its elements, and soon ready 

 to be used again as food by succeeding generations. 



This second form of reproduction rendered possible cross-fertili- 

 zation, which has proved to be a prime factor in enabling life to 

 evolve from primitive types, through its various phases up to existing 

 forms. Sexual differentiation, and the various contrivances for 

 preventing self-fertilization, and at the same time favouring cross- 

 fertilization, which have been brought so prominently before the 

 public in connection with flowering plants, and popularly believed 

 to be peculiar to the higher forms of life, are to be met with 

 in the various groups of algae ; the structural differences in this 

 ■ matter between algae and phanerogams being the result of the 

 markedly different conditions under which they respectively exist. 

 Alga?, in common with all cryptogams, depend on water as the 

 motor agent by which the union of the two bodies connected with 

 sexual reproduction is effected ; consequently the various struc- 

 tures that enable flowering plants to utilize the wind or insects 

 as agents in transporting the pollen to the stigma are absent 

 from the former. 



In algae, again, we trace the evolution from primitive isolated 

 unicellular forms, as Eremosphsera, to the more complicated multi- 

 cellular types, illustrated by the brown and red seaweeds, showing 

 marked differentiation and division of labour, through the numerous 

 stages of cell-colonies composed of unicellular organisms each 

 retaining its original morphological and physiological characteristics, 

 but mechanically held together by mucus. In the Florideae, if we 

 except a few minute parasitic forms included by Eeinsch* on account 

 of their red colour, all the members are multicellular, but, as 

 described above, consist in the simplest types of threads composed 

 of a single row of cells placed end to end. In addition to the 

 sexual reproductive organs, a very characteristic and more universal 

 vegetative method occurs, consisting of the contents of certain cells 

 breaking up when mature into four portions, hence known as 

 tetraspores or tetragonidia. It is remarkable that the exact method 

 of reproduction characteristic of the lowest forms of plant life 

 should reappear in this highly developed family and its near 

 relation Dictyotese, after having been superseded in the higher 

 green and in all the brown seaweeds. Tetrasporic individuals are, 

 with very rare exceptions, distinct from those bearing sexual organs. 



* Reinscb. torn. cit. 



