- 植物分類・地理 (ISSN:00016799)
- vol.33, pp.179-189, 1982-04-20
1) Conocephalum supradecompositum, annual species restricted to the northern part of East Asia, is considered to be derived from C. conicum, perennial species widely distributed throughout temperate regions of the Northern Hemisphere. 2) C. supradecompositum produces in autumn numerous gemmae endowed with a strong resistance to cold and dryness. The gemmae are modified branches of the thallus ; prior to formation of gemmae, the thallus performs frequent dichotomous branching, and the terminal dichotomy itself is transformed into a gemma. Thus, each gemma has two growing points covered with scales, and it exhibits a strong, inborn dorsiventrality in germination. 3) C. supradecompositum is unique among bryophytes in cylindrical, sausage-shaped spore mother cells, linear spore tetrads, and dimorphic spores. 4) The genus Conocephalum is very characteristic in elaters ; elaters in a capsule are 2-3 times as many as spores (in other genera of the Hepaticae, the number of elaters is far smaller than that of spores) ; and they show an extremely wide range of variation in size, shape, and number and orientation of spiral thickenings-and there occur rarely elaters with dextrorse spiral thickenings (so far as examined by the writer, the spiral thickenings of elaters are universally sinistrorse in other genera of the Hepaticae). The exceptional dextrorse elaters are assumed to be induced from the originally sinistrorse ones through conversion of the axis as shown in Fig. 3, x-z'.