vi INTRODUCTION. 
in greenhouses and hothouses, warm springs, outlets of warm 
water from steam engines, brackish ditches, all these have their 
own peculiar forms, and experience will soon prove that where 
the favourable condition of quiet humidity is found, search will 
seldom be in vain. Of course, during exceptionally dry 
weather localities which would otherwise give satisfaction may 
produce nothing but disappointment. 
The methods of collecting do not much differ from those 
adopted for other kinds of pond life. A japanned case with 
from six to twelve corked test tubes will usually suffice for a 
day’s collecting. Filamentous Alge, such as Spirogyra, Clado- 
phora, &c., may be wrapped singly in paper, and a number of 
these packets can be contained in a small tin box. It is always 
essential to keep each “ gathering ” by itself. 
Preservation for future study, or for the herbarium, will be 
secured by the usual methods of floating and mounting marine 
Alge, first cleansing the specimens by well washing in a flat 
dish or soup-plate, and finally passing under them a slip of 
clean white paper, which is raised so as to take up the Alg@ in 
the middle, well floated into position, draining off the water, 
and then drying, with the least pressure possible. For minute 
species, and small specimens, thin flakes of mica are preferable 
to paper, for many reasons, especially that they can be placed at 
any time under the microscope and examined. The Palmel- 
lacee, and similar groups, will be of very little service if dried 
in any other way. Most species will adhere of themselves to 
either paper or mica, the exceptions, such as Vaucheria and some 
Cladophore, can be fixed with gum tragacanth. 
Some difficulty may probably be experienced in mounting 
satisfactorily specimens for the microscope. We have seen 
“ slides” in which the specimens were still green and life-like 
after having been mounted for twelve years in the water in 
which they were collected, but unfortunately there is always a 
risk of leakage with mounts in fluid, If the medium is denser 
than the contents of the Alge cells, the endochrome will be 
contracted and the walls collapse. One objection to mounting 
in glycerine, or glycerine and water, is the density of the 
medium, and consequent collapse of the cells ; another, that in 
