DEVELOPMENTAL CYCLES IN SHOOT GROWTH OF MALE CYCAS CIRCINALIS

Cycles of development in several male shoots of Cycas circinalis were studied by counting sequences of foliage leaves, scale leaves, and cones by observation of either their scar patterns or vascular remains. Although male cones are always produced subsequent to a cycle of foliage leaves and are fairly regularly spaced there is no obvious correlation between their presence and the previous cycles of leaves. Ratios of foliage leaves to scale leaves in each cycle are variable. The primary diameter of the axis is obconical, but a conical stem form results from secondary growth. The result of concentric development of xylem and phloem is positively correlated with stem diameter rather than stem age.