VARIATIONS IN THE NUMBERS OF SCALES, POLLEN SACS AND POLLEN GRAINS OF THE MALE FLOWERS OF CRYPTOMERIA JAPONICA

Abstract

The structure of male flowers of Cryptomeria japonica D. Don, which consist of scales, pollen sacs and pollen grains, was studied using samples from five stands of different ages and origins of seedlings or rooting, and the methods for estimating the number of pollen grains contained in a flower were discussed. Each scale bears between 0 and 7 pollen sacs, with a mode of between 3 and 5 pollen sacs for each stand, the number varying according to stand age. The number of pollen grains per scale increases with the number of pollen sacs present. The mean number of pollen grains per single pollen sac for scales bearing three or more pollen sacs has a constant value in each stand and each year. When restricted by a small sample size, the multiplication of this constant value by the total number of pollen sacs per flower gives a useful estimate of the number of pollen grains contained in a flower. A rough estimate of the number of pollen sacs per flower may be obtained by using the proportional relationship between the total number of pollen sacs and scales on both a stand and year basis. The total number of pollen sacs per flower in the age sequence of stands consisting of seedlings grown from seeds declines with increasing stand age. However, the flowers from a young stand planted with short trees by rooting have the same number of pollen sacs as those from the mother stand. No rejuvenescence of male flowers is found in young trees that have been propagated vegetatively.