99 
Dec. 31 , 1909 . The .Queensland Naturalist 
which study they will receive the most valuable assistance 
from F. M. Bailey’s Botany Bulletins, Nos. VI. and XI. 
I would also add that I should be most happy to lend any 
aid in my power to any member of the society who found 
a difficulty in the identification of his species, for though 
I distinct!}^ disclaim any pretension to be regarded as an 
authority in Spirogyra, I have nevertheless made a 
speciality of the study of this genus for about four years, 
and have procured, at great cost and trouble, the great 
mass of the literature of the subject which I have found 
sufficient for the identification of every species which has 
come in my way. 
As already stated, it is necessary to obtain specimens 
both of the sterile and conjugial filaments in order to deter- 
mine the species. The sterile, or vegatation specimens,, 
should first be examined, and the partition walls between 
the cells attended to. If the cells are separated by a par- 
tition, that is, a plane transverse section of the filament,, 
the species belongs to the section “ Cells with the ends 
truncate,” but if the dividing wall is folded back, as already 
described, the species must be referred to the section “ Ceils 
with the ends replicate.’’ The number of spirals must 
next be ascertained. To do this, it is not sufficient to observe 
a single filament and draw the conclusion therefrom ; for 
example, hundreds of filaments belonging to one species 
may contain but one spiral, but upon further search odd 
threads may be found interspersed among them with two, 
or even three spirals, and this circumstance is of importance 
in making out the diagnosis. The least and greatest number 
of revolutions described by the spirals, observed in cells 
the most unlike in length and density of spiral convolutions, 
which different filaments exhibit, must also be recorded 
with exactness, with their general tendency, whether to 
laxity or density. By the aid of an eye-piece micrometer, 
and a scale, previously made, which indicates the actual 
value of the divisions of the micrometer when projected 
on to the field of the microscope, the thickness of the 
filaments must be measured, and their maximum and mini- 
mum diameter noted down ; also the range of multiples 
which the length of the ceils gives of their breadth. The 
dimensions are most conveniently expressed in micro- 
millemetres, this unit being the one-millionth part of a 
metre, the sign for which is the Greek letter mn (^). The 
description of the sterile threads being now complete, 
specimens in fruit should next be mounted. The length 
of the fertile cells compared with that of the sterile cells, 
and with that of the spore, as also the fact of the spore- 
bearing cells being swollen or otherwise, must be deter- 
mined ; and lastly, the description of the spore must 
embrace its shape, colour when mature, range of diameter 
