1894.] Pollen Grain and the Nutrition of the Pollen Tube. 125 



The object of the present research was to isolate these enzymes 

 and to investigate any changes in the amount of either of them during 

 the progress of the germination. Further, to ascertain something of 

 the metabolism going on in both the pollen grain and the style in the 

 interval between pollination and fertilisation. 



Both the enzymes were prepared from bruised grains by the use of 

 the ordinary solvents water, glycerine, and solutions of common 

 salt the latter being, perhaps, the most efficient. Details of the 

 experiments, and the conditions of extraction, are given in the paper 

 of which this is an abstract. Diastase was found in the resting 

 pollen of various species of Lilium, Helianthus, Gladiolus, Anemone, 

 Antirrhinum, Tropceolum, Pelargonium, Crocus, Brownea, Helleborus, 

 Alnus, Tulipa, and Olivia, and in that of Zamia after germination had 

 begun. The diastase is in the form of the translocation diastase of 

 Brown and Morris. Invertase was found in the pollen of Helleborus, 

 Narcissus, Ricliardia, Lilium, and Zamia. Some of these species 

 contained both enzymes. 



During the germination of the pollen grain the quantity of both 

 enzymes was found to show a considerable increase in amount, in 

 some cases even four or five fold. This increase was estimated by 

 noting the diastatic or invertive power of extracts prepared -side by 

 side, from weighed quantities of pollen, and from equal quantities 

 allowed to germinate in various culture fluids. Control experiments 

 were carried out to show that the increase of enzyme action was not 

 due to a more complete extraction of the ferment from the thin- 

 walled tube than was possible from the thick-walled grain, but that 

 there was an actual total increase of the enzyme. In one case there 

 was noticed a diminution of ferment in the earliest stages of the 

 germination, which may probably be correlated with the digestion of 

 the starch grains of the grain, or of some portion of them, before the 

 output of the pollen tube. It was found, further, that when the 

 power of germination of the pollen grain was becoming feeble, from 

 its being kept for some weeks, there was a very considerable diminu- 

 tion of the amount of diastase that could be extracted. Full details 

 of these experiments are given in the paper. 



The mode of growth and nutrition of the pollen tube was investi- 

 gated by culture of the grain in hanging drops of fluid in a moist 

 chamber, and by chemical analysis of the contents of various pollen 

 rains and styles. 



The microscopic examination of pollen tubes revealed general 

 .nularity of their contents, with the formation of certain large and 

 refringent granules, that were apparently extruded regularly by the 

 tube at definite places near the top. This appearance has already 

 been noticed by Van Tieghem, to whose work reference is made. 

 The extrusion of these granules suggests that they are the medium 



