536 Pier cy.— The Structure and Mode of Life of a 
starch is frequently absent from granular cells. It is possible that there is 
a more direct relationship between the production of starch and the special 
substance referred to on p. 532. Thus they are usually either both abundant 
or both scanty. In the second desiccation experiment, starch remained 
in quantity as long as there was any appreciable amount of this substance, 
but tended to disappear as the latter became scanty. The relation between 
this substance, starch, and granules is, however, still obscure. 
6. Summary. 
A general account is given of the life of a form of Hormidium flaccidum 
in its native habitat. The survival of the vegetative filaments throughout 
successive seasons of the year is described, and the modifications to which 
they are subject during periods of drought, chiefly the accumulation of 
refractive granules, and changes in the longitudinal walls and septa, 
examined. 
A detailed description is given of the two common methods of repro- 
duction possessed by the Alga, viz. (i) transverse splitting of the filaments 
at the septa, and (ii) production of aplanospores. Regarding (i), a general 
breaking up of the filaments into isolated cells or few-celled pieces has not 
been observed, splitting occurring at points in a filament some considerable 
distance apart, though in favourable circumstances a minor proportion of 
the filaments have become divided into few-celled fragments. It is suggested 
that splitting is due to the effects of renewed turgor on desiccated filaments 
in which degeneration of the cuticle or weakening, caused by the develop- 
ment of mucilaginous substance between the two lamellae of the septa, has 
taken place. It is indicated that the production of aplanospores occurs in 
all seasons of the year, but is dependent on an ample supply of water. 
Cells giving rise to aplanospores usually contain an abundance of the special 
substance referred to on p. 532 and also granules. 
A white refractive substance, which appears in the cells under certain 
conditions in the form of granules and rounded masses, is described. This 
is shown to arise chiefly in the region of the polar vacuoles, but also sparsely 
distributed in the peripheral protoplasm. Two conditions have been 
observed to favour its production, viz. (i) drought, (ii) a plentiful supply of 
carbohydrates, e. g. glucose. It appears to be associated with a second 
special substance in the cell (cf. p. 532) and is possibly formed as a result 
of concentration of this substance. Since, in suitable circumstances, the 
cells are capable of eventually absorbing the granules, they evidently 
function as a reserve food. 
It is shown that during the first weeks of a period of drought the 
death-rate decreases, while the abundance of granules increases to a 
maximum. When growing in its native habitat, the Alga in all probability 
