Historically, hemp has been an important economic crop, yet in the absence of deposited achenes or fibres, it is difficult to infer local hemp cultivation and/or on-site retting from variations in the values for Cannabis saliva pollen. From work in Finland, it has been suggested that lower Cannabis pollen percentages in some areas may be due to the practice of removing male hemp plants while weeding, and leaving the female plants which were apparently preferred for their fibre-producing qualities. In other geographical areas, there was no sexual selection of plants, thus enabling the pollen from male plants to be introduced more abundantly into retting pools. In this paper, the bases of this supposition arc questioned, and it is suggested that in some areas, differences in the timing of anthesis and cropping/retting may explain some of the percentage variations observed in the pollen record.
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