( 188 J 
certain degree of concentration, which solution might be cailed a 
stigmatic fluid of the simplest composition. 
It is likely that among these different kinds of pollen there may 
occur some, — if at least concentration be not too high — whieh 
by a too energetic absorption of water burst at once, and whose 
contents stream out into the liquid in the same way as is seen with 
many species of pollen brought into pure water. Among the species 
of pollen which do not burst there are some which increase in size 
under absorption of water. 
Pollen-grains which in the dry state are elliptical, such as those 
of Hemerocallis fulva, Torenia Fournieri, Digitalis purpurea, Mauran- 
dia erubescens, are rounded thereby into balls. 
A few species form their germinai tubes !) in the fluid, and finally, 
there are some which not only don’t germinate but neither suck 
water from the liquid, and retain the shape and size which they 
possessed in the dry state. The higher the degree of concentration, 
the less the pollen-grains are able to draw water from the saccharose 
solution. 
Also pollen-grains of plants of the same genus frequently possess 
in a very different degree the power to absorb water from a solution 
of saccharose. 
1) It is known that many species of pollen which do not germinate in water, may 
be induced to do so in solutions of sugar, agar-agar, gum, dextrine, or in mixtures 
of these substances in a certain degree of concentration for each species. Here- 
about informations have been given by Van Timauem a), Kwny 4), StRASBURGER c) 
and Mouiscu d). 
Morisen determined for 60 plants the degree of concentration which should be given 
to the canesugar solution in order to call forth the germinal process. From his state- 
ment it appears that there are pollen species which no more germinate when the 
saccharose solution is higher than 2 pCt. (Platanthera bifolia) or 5 pCr. (Allium 
ursinum), Whilst some can still germinate in solutions of 40 pCt. a few even in 
solutions of 50 pCt. (Zpipactis latifotia, Lilium Martagon). It is now supposed that 
this proves that special relations of nutrition govern the germination, and that distinct 
species of pollen have in this respect distinct requirements. However, considering the 
fact that a great many pollen-grains want no food at all to germinate, and that others 
form their germinal tubes in water with addition of a special chemical substance, 
which can serve as a stimulus, it is my opinion that we should rather think here 
of an adjustment for the absorption of water required for the germination. 
a) Annales des s. c. nat, Bot, 5me Série, tome XII, 1872. 
b.) Sitzungsber. des bot. Vereins d. Provinz. Brandenburg XXXIIL, 1881. 
c.) STRASBURGER, Neuere Untersuchungen ueber den Befrüchtungsvorgang bei den 
Phanerogamen, etc. Jena, 1884, Prinasneim’s Jahrb. Bd. XVIII, 1886. 
d.) H. Morrscu. Zur Physiologie des Pollens. Sitzungsber. der math. naturw. Classe 
der K. Akademie dor Wissensch. Wien. Bd. CIL, Abth. I, 1893. 
