n = 5. Figs. 22-29
In section Tristichophyllum the type and sole species is H. diversifolium. Touw (1971) described it as one ofthe most beautiful and striking species in the family. The capsules are large, 4.5-6.0 mm long, and the leaves have a distinctly tristichous arrangement. It is a common species in Papua New Guinea, its center of variation (Touw, 1971) and where the specimens examined here were collected. The name typifies the extreme variability of this species, which has a primarily Malesian distribution and does not extend south into Australasia.
The chromosome number obtained from three populations was determined as n = 5 (Figs. 22, 28). This was based on studies of both meiosis and premeiotic mitosis. The five bivalents have been aligned (Figs. 23, 29), those in Fig. 23 being smaller than those in Fig. 29. They consist of one slightly larger, three medium and one smaller bivalent. The investigation of the mitotic complement gives a much clearer picture ofthe actual sizes of the chromosomes in the basic genome (Figs. 24 & 26) from two separate populations. These have been aligned (Figs. 25 & 27) for analysis of chromosome types. There is clearly one large chromosome pair which stands out, one member metacentric, the other sub-metacentric. The rest can be divided into three pairs of intermediate sized chromosomes, one pair submetacentric the others metacentric, while the smallest chromosome appears to be metacentric.