
40 BOTANICAL GAZETTE [JANUARY 
significance that the pollen of so many species of plants germi- 
nate either in sugar solution or in water. According to Molisch* 
many forms germinate best in about Io per cent. sugar solu- 
tion, and concentrations of from 15 to 40 per cent. are often 
required. This might suggest an osmotic stimulus. Neverthe- 
less, there are many forms germinating well in water, and for 
other forms perhaps the idea of a special stimulus should be 
further applied to a study of pollen. Molisch indeed found 
minute quantities of malic acid a stimulus to the germination of 
Ericaceae; but, in general, my results indicate that it is only a 
stronger stimulus than pure water, not equal to sugar, for 
example. 
Lidforss’ has recently made extensive studies with pollen 
germination in ‘‘pure water,” and among many plants whose 
pollen is so adapted may be mentioned Orchidaceae, Salicaceae, 
and many Liliaceae, Geraniaceae, etc. Following in the path of 
still earlier workers along that line, Borcodin® clearly indicated 
that light has a stimulating effect for the germination of fern 
spores. Kny’ and others further determined the necessity of 
this factor. Heald® has more recently shown that this stimulus 
may find a substitute in high temperatures; and apparently he 
has also cleared up some previous inconsistencies. In the same 
paper, Heald has demonstrated the necessity of light for the 
germination of moss spores. In a nutrient solution containing 
peptone or sugar, on the other hand, good germination resulted 
in yi and higher temperatures alone had no stimulating 
OLISCH, H.: Zur Physiologie des Pollens mit besonderer Riicksicht auf die 
p laeatiaree Bewegungen der Pollenschlauche. Sitzb. d. kaisl. Akad. d. Wissen- 
schaften zu Wien 102': 423-427. 1893. 
5 LipForss, B.: Weitere Beitrage zur Biologie des Pollens. Jahrb. £. wiss. Bot. 32; 
237-312. 1899. 
° Boropin, —: Bull. de l’Acad. imp. de St. es 433-440 1867, (ref. 
Heald, 1. c.). 
7 Kny, L.: Beitrage zur Entwickelunsgeschichte der Pasnereuet: Jahr. f. wiss- 
Bot. 8: 1-15. 1877. 
* HEALD, F, pE F.: Gametophytic regeneration exhibited by mosses and condi- 
somo for the germination of cryptogam spores. Inaugural-Dissertation. Leipzig, 
1897. ; 

