THE MICROSCOPE. 363 
Canadensis has grains in groups of four, or two, which measure 
as much as 258py. 
Some of the most interesting grains for study in sulphuric 
acid are those of Lychnis Githago, Saponaria officinalis, the Mal- 
lows, the Evening Primrose, the Heaths,:not forgetting Tilia 
already mentioned. Helianthemum Canadense has the grains in 
groups of four, like the Heaths, but the grouping differs from that 
of Anacharis where the grains are arranged side by side, while the 
Heaths have the fourth above the three as a foundation. Lychiis 
has the numerous perforations in the extine covered with hem- 
ispherical lids, which come off on immersion in sulphuric acid, 
an interesting sight, and exceptional. 
In closing I would put the following questions, to be answered 
by future observation: First, in case that ten per cent. of the 
pollen grains burst readily in water, how far would a wet season, 
or a rain at the time of pollination, prevent, or would it in any 
measure prevent, the formation of the pollen tube, and thus 
make fertilization impossible? Secondly, what is the difference 
in the chemical composition of the extine, if any, which causes 
the change of color that takes place when certain grains are im- 
mersed in sulphuric acid? 
A single drop of blood contains about two and one-half mill- 
ions of red corpuscles. 
An organic being is a microcosm, a little universe formed of a 
host of self-propagating organisms inconceivably minute and as 
numerous as the stars in heaven.—Darwin. 
Parasites are not usually reproductive in the animal which 
they inhabit. They respect the hearth which shelters them, and 
their progeny are not developed by their side. The eggs are ex- 
pelled with the feces, and sown at a distance for other hosts.— 
Van Beneden. 
There is scarcely any well-informed person who, if he has but 
the will, has not also the power to add something to the general 
stock of knowledge, if he will only observe regularly and meth- 
odically some particular class of facts which may most excite 
his attention, or which his situation may best enable him to 
study with effect—Sir John Hirschel. 
