I20 
but only as a last resource have the authors had recourse 
to reproductive structures as a means of distinguishing 
one genus from another. It is frankly admitted that the 
result is a distinctly unnatural association of groups of 
genera—a condition of affairs to be deplored but excusable 
perhaps on the score of convenience. In extenuation of 
the policy it may be urged that natural families of algae 
are founded largely on reproductive structures which may 
not be present on the material a student wishes to identify. 
Worse than that, discrimination between algal families 
sometimes rests on developmental history of complicated 
reproductive structures, as for example, the cystocarps of 
the Rhodophyceae. Scrutiny of the mature reproductive 
plant will yield no evidence of past phases of its develop- 
ment, and to build a key for the use of general botanical 
students on any such plan would be to assume a theoretical 
knowledge they might not possess and thus defeat the 
object of the key, which is to enable the student to arrive 
with the minimum of mental effort and the maximum 
precision at a correct identification of his plant. 
It must be stated with emphasis that the key is only 
built to cover the genera as represented by the species 
present in the flora of the district under discussion. The 
use of the key for the flora of another area may lead the 
student into some difficulty. 
CHLOROPH YGEAE. 
1. Microscopic endophytes or epiphytes; or, if independent 
plants, not taller than 3 cms. when mature ... 2 
Macroscopic plants discernible to the naked eye as adie 
or conjointly forming conspicuous masses... sis — - 
2. Independent plants attached to rock surfaces ... ome <- ae 
Epiphytes or endophytes ... Se ee a: sae <a 
3. Plants single “celled,’’ tubular, club-shaped with a long, 
tapering, colourless stalk ies = Codiolum ...p. 45 
Plants membraneous, ovate or lanceolate, stalked, cells in groups 
or packets embedded in colourless matrix Prastola ...p.45 
(See note I, p. 105.) 
Plants tubular, branched or unbranched ... Sys ae — | 
