天南星科的生态地理和起源

本文将天南星科105个属的分布区归纳为12个分布类型和29个亚型，对每一类型的属进行生态地理分析。本科计有88个热带属，占全科的83．8％，是一个热带科。全科有两大分化中心：热带亚洲为属的多样化中心，热带美洲是种的分化中心。根据天南星科各属的生态地理研究，结合到科的系统发育程序，作者得出结论说：天南星科的原始类群在晚白垩纪时起源于亚洲大陆南缘，即欧亚古陆的亚洲南缘地带的水域生态环境。

EMBRYONIC EXPLANT CULTURE ON LYCORIS AUREA

The present paper deals with the cytological invcstigation of Dys- osma pleiantha (Hance) Woodson, which is a chinese medicine and endemic to China. The karyotype of the specics is reported here for the first time. Accor- ding to the terminology defined by Levan et al. the karyotype formula is K(2n) =8m(2SAT) + 2st(SAT) + 2t. It belongs to "2A" of Stebbins'' karyo- typic symmetry and is generally regarded as a more primitive one. Measure- ments of the chromosome complement and the idiogram of the karyotype are given in Table l and Fig. 2 respectively.