NOTES. 
ON THE GERMINATION OF THE POLLEN-GRAIN 
AND THE NUTRITION OF THE POLLEN-TUBE ' The 
germination of the pollen-grain, leading to the protrusion of a pollen- 
tube, suggests, at once a process analogous to the formation of the 
pro thallium of the Vascular Cryptogams. Its peculiar situation and 
the fact that it has to make its way, unlike the latter, through a mass 
of tissue, suggest however certain peculiarities attending its nutrition. 
The absence of chlorophyll and the probable richness of the en- 
vironment in various elaborated materials makes it probable that the 
progress of the tube downwards through the style is attended by 
a process of intra- or extra-cellular digestion, depending on the 
occurrence and activity of enzymes. 
It has been shown by various observers that pollen-grains allowed 
to grow in solutions of cane-sugar speedily bring about the appear- 
ance of a reducing sugar. Even when germination has been in- 
hibited by antiseptics, the same inversion of the cane-sugar has been 
observed to take place. Certain grains again when cultivated in 
weak starch-paste have been shown to liquify it, with formation of 
maltose. 
The research which forms the subject of the present paper was 
directed first to the preparation and identification of digestive enzymes 
from pollen, and to the variations in their amount which attended the 
progress of the pollen-tube through the tissue of the style. 
Both diastase and invertase were found to exist in various pollens ; 
some containing both, some only one of the two. To extract them 
the pollen was collected from dehiscing stamens, bruised in an agate 
mortar, and extracted with various solvents, usually 5 per cent, of 
NaCl. As an antiseptic during the digestions, *2 per cent. KCy was 
found most serviceable. 
1 Abstract of a paper read before the Royal Society, February 8, 1894; see also 
Annals of Botany, Vol. v. 1891. 
