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The relation was studied between vegetational development and soil formation in the Pleistocene cover sands in the Netherlands, particularly whether forests, rather than heaths, were early involved in the formation of podsolic soils. The pollen content of profiles of various podsols and some gleys were examined, all lying below layers of drift sand and peat of various ages. Beyerinck's palynological method had to be extended with a study of the significance of sand diagrams. In an undisturbed podsol pollen decreased in concentration roughly geometrically from the sand surface downward.A relation could be observed between the length of the vertical distribution of pollen (pollen profile) and the depth above, in which the original stratification of the Eolian cover sand had entirely disappeared.It was concluded that most of the pollen permeated before podsolisation, during the biologically very active stage of the homogeneous forest profile. The lowest part of the pollen profile, already fixed, constantly 'grew' on the top through addition of continually younger spectra; in later degradation stages illuviation of pollen could also become significant. A paucity of tree pollen in the whole spectrum could occur after various types of vegetation and after certain conditions of soil moisture.During the Boreal, Atlantic and Fagus-Carpinus period both homogeneous forest profiles and podsolic profiles occurred under diverse vegetation. During each of these periods homogeneous forest profiles were degraded to new podsolic profiles.

Germination of pear pollen markedly improved when boric acid was added to the medium. The pollen was more sensitive to boron in water than in 10 % sugar solution. Supplying weak solutions of boron to pear branches before flowering resulted in a good germination of the pollen in sugar solution without boron. Spraying apple-trees and pear-trees with boron solutions had no significant effect on fruit set, despite the pollen sensitivity to boron in vitro.The amount of boric acid in the medium determined percentage germination (saturation curve) and length of pollen tubes. Boron was not required until the tubes protruded. Temperature and sugar concentration both showed optimum values for germination. The effect of boron on germination rate was positively correlated with temperature and negatively with sugar concentration. An increase of 10°C roughly doubled this influence on germination rate. Germination was positively correlated with pollen grain number per drop, whether or not boron was present. So the mutual stimulation of the pollen was more effective with boron or with pollen from rather boron-rich branches. Pollen extracts in 10 % sugar solution with or without boron stimulated germination (also of other species).Both apple and pear pollen (and those of many other species) remained viable longest at both low humidity and temperature. In deep-freeze longevity was more than 2 years at -180°. Viability remained unchanged. Longevity would probably have been indefinite.

Germination of pear pollen markedly improved when boric acid was added to the medium. The pollen was more sensitive to boron in water than in 10 % sugar solution. Supplying weak solutions of boron to pear branches before flowering resulted in a good germination of the pollen in sugar solution without boron. Spraying apple-trees and pear-trees with boron solutions had no significant effect on fruit set, despite the pollen sensitivity to boron in vitro.The amount of boric acid in the medium determined percentage germination (saturation curve) and length of pollen tubes. Boron was not required until the tubes protruded. Temperature and sugar concentration both showed optimum values for germination. The effect of boron on germination rate was positively correlated with temperature and negatively with sugar concentration. An increase of 10°C roughly doubled this influence on germination rate. Germination was positively correlated with pollen grain number per drop, whether or not boron was present. So the mutual stimulation of the pollen was more effective with boron or with pollen from rather boron-rich branches. Pollen extracts in 10 % sugar solution with or without boron stimulated germination (also of other species).Both apple and pear pollen (and those of many other species) remained viable longest at both low humidity and temperature. In deep-freeze longevity was more than 2 years at -180°. Viability remained unchanged. Longevity would probably have been indefinite.

The relation was studied between vegetational development and soil formation in the Pleistocene cover sands in the Netherlands, particularly whether forests, rather than heaths, were early involved in the formation of podsolic soils. The pollen content of profiles of various podsols and some gleys were examined, all lying below layers of drift sand and peat of various ages. Beyerinck's palynological method had to be extended with a study of the significance of sand diagrams. In an undisturbed podsol pollen decreased in concentration roughly geometrically from the sand surface downward.A relation could be observed between the length of the vertical distribution of pollen (pollen profile) and the depth above, in which the original stratification of the Eolian cover sand had entirely disappeared.It was concluded that most of the pollen permeated before podsolisation, during the biologically very active stage of the homogeneous forest profile. The lowest part of the pollen profile, already fixed, constantly 'grew' on the top through addition of continually younger spectra; in later degradation stages illuviation of pollen could also become significant. A paucity of tree pollen in the whole spectrum could occur after various types of vegetation and after certain conditions of soil moisture.During the Boreal, Atlantic and Fagus-Carpinus period both homogeneous forest profiles and podsolic profiles occurred under diverse vegetation. During each of these periods homogeneous forest profiles were degraded to new podsolic profiles.