. Dansk botanisk arkiv. Plants; Plants -- Denmark. 10 Dansk Botanisk Arkiv, Bd. 2 Nr. 10. Besides, the rapid penetration of fluids into the pollen-grains of the projection may be proved in another way. Pollen-masses are, immediately on being taken out of the flower, yellow to the naked eye, owing to the colour of the wall of the pollen-mass; but under the microscope they prove to be greyish and opaque. Their greyish appearance is due to the water in the pollen-grains, for on remaining exposed to the air the greyish appearance is lost; it reappears however on the pollen-mass being placed in a v
. Dansk botanisk arkiv. Plants; Plants -- Denmark. 10 Dansk Botanisk Arkiv, Bd. 2 Nr. 10. Besides, the rapid penetration of fluids into the pollen-grains of the projection may be proved in another way. Pollen-masses are, immediately on being taken out of the flower, yellow to the naked eye, owing to the colour of the wall of the pollen-mass; but under the microscope they prove to be greyish and opaque. Their greyish appearance is due to the water in the pollen-grains, for on remaining exposed to the air the greyish appearance is lost; it reappears however on the pollen-mass being placed in a vessel saturated with vapour. Desic- cated pollen-masses appear to be yellow also under the microscope, be- sides being pellucid, owing to an oil in the grains of pollen. If a desicca- ted pollen-mass is put into water or in a vessel sa- turatedwith vapour, the pollen-mass is seen under the microscope to become greyish, first where the chink is later on formed, and the greyish appearance from there to spread into the pol- len-mass. Thus liquids are proved to penetrate most rapidly into the grains which are lying just inside the chink, and to penetrate from here quickly into the other grains of the pollen-mass. Further it is shown that the difference in pene- trability in the different parts of the wall most probably is related to a difference in the chemical nature; but by this the cause of the formation of the chink has not been found; for we must here emphasize that the chink of the pollen-mass in Asclepias cornuti when being upon the stigma or in strong sugar solutions, is not made until long after the surrounding liquid has penetrated into the pollen-mass, so that all the grains are able to become turgid before the chink is formed. So the formation of the chink cannot be due to the fact, that the chink-forming grains of pollen become turgid before the rest of the grains of pollen. The joint pressure of the grains of the pollen-mass is of no- consequence for the formation of
Size: 1540px × 1623px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectio, bookdecade1910, booksubjectplants
