Studies on the Chromosome Numbers in Campanulaceae

Abstract

1. Campanuleae has about 31 genera, of which 12 have been studied cytologically and their meiotic chromosome numbers were counted by the writer.The genera and number of species studied by the writer are as follows:2. Campanulinae has about 12 genera, 7 of which have been studied cytologically by the writer; namely Campanula, Symphyandra, Adenophora, Specularia, Michauxia, Trachelium and Phyteuma. The chromosome number 17 seems to be the universal one, because the majority of genera in the Campanulinae has 17 or its multiples. From the previous karyological results the diversity in chromosome numbers is only found in Campanula and Phyteuma where 8 and 17 are found in the former and 18, 13, 12, 17, 5 in the latter.3. The genus Campanula has two groups whose chromosome numbers are different; viz. 8 and 17. While the multiples of 17 are abundantly found, those of 8 are rather rare. To date the meiotic chromosome number 16 has been only found by Gairdner (1926) in C. persicifolia “Telham Beauty” and by de Vilmorin and Simonet (1927) in C. isophylla.From the following considerations these two groups seem to have been derived quite independently of each other:a) If the n=17 group had been derived from the n=8, the former would have larger epidermal cells than those of the latter. But in reality, the epidermal cells of the leaves of the former are smaller than those of the latter.b) The n=8 group has generally linear lanceolate stem-leaves, and up to this time we have not found other than linear lanceolate leaves in the plants having the meiotic chromosome number 8.c) We do not find any similarity in the outer appearances between n=17 and n=16 groups, but we find it among plants having 8 or its multiple chromosomes and also among plants having 17 or its multiples.d) It is very interesting that there are no 8 groups in Adenophora, Symphyandra etc., though they are systematically very closely allied to Campanula.These facts show that we cannot say that 17, which is universally found in Campanulinae is derived from 8. On the contrary, the 8 group can be said to be independent of Campanula having n=17.4. Wahlenbergiinae has about 16 genera, of which 4 had been studied cytologically and their meiotic chromosome numbers were counted.5. Platicodinae has only one genus. Our cytological observations show that it is probably of hybrid nature.