<P> For most species found in Australia, male and female cones occur on the same plant (tree or shrub), with female usually on the higher branches towards the top of the plant . This distribution is thought to improve chances of cross-fertilization, as pollen is unlikely to be blown vertically upward within the crown of one plant, but can drift slowly upward in the wind, blowing from low on one plant to higher on another plant . In some conifers, male cones additionally often grow clustered in large numbers together, while female cones are more often produced singly or in only small clusters . </P> <P> A further characteristic arrangement of pines is that the male cones are located at the base of the branch, while the female at the tip (of the same or a different branchlet). However, in larches and cedars, both types of cones are always at the tips of short shoots, while both sexes of fir cones are always from side buds, never terminal . There's also some diversity in bearing in Cupressaceae . Some, Cupressus for instance, has little or no differentiation in the positions of male and female cones . </P> <P> Cone crop potential can be predicted in various ways . An early indication of a potential crop can be a period of abnormally hot, dry weather at the time of bud differentiation, particularly if the current and preceding cone crops have been poor (Nienstaedt and Zasada 1990). Estimates of cone crop potential can be made by counting female reproductive buds in fall or winter, and an experienced observer can detect the subtle morphological differences and distinguish between reproductive buds and vegetative buds (Eis 1967b). </P> <P> White spruce seed collection is expensive, and collection from cone caches of red squirrels is probably the cheapest method . The viability of seed from cached cones does not vary during current caching, but viability drops essentially to zero after being in caches for 1 or 2 years (Wagg 1964). </P>

Where is the male gametophyte located in conifers