The Nucleolar Chromosome in Hepatics.: II. A Phylogenetic Speculation

Differential Evolutionary Activity in Bryophytes

“…This would imply that the hepatics with n = 9 have arisen by duplication from a lower chromosome number. Berrie (1958) noted two nucleolar chromosomes in the gametophyte of Riccardia pinguis, and on this basis considered this to be diploid. The fact that the number of nucleoli is an indication of ploidy was originally pointed out by Gates (1942).…”

“…Liverworts.-The chromosome numbers of liverworts are listed comprehensively by Berrie (1960) and in the Index of Plant Chromosome Numbers (Cave, 1956(Cave, -1963. On the basis of these lists the data on basic chromosome numbers are available for 325 liverworts.…”

“…It is clear from these examples that the number of nucleolar chromosomes is not always a reliable indication of ploidy. More recently, Berrie (1963) has added a further argument in support of his hypothesis regarding the presumed diploid nature of liverworts on the ground of "evident resistance of hepatics at higher level to further polyploidy." The diploid level of ploidy in the gametophyte is not high enough to be considered a significant hindrance to further polyploidy.…”

“…From the statement of Allen (1935) it appears that the proportion of the dioecious and monoecious species in bryophytes is probably half and half. On the basis of Stephani's work, Berrie (1963) has made a survey of the monoecious and dioecious genera in liverworts. According to him the majority of the genera are mixed, i.e., they contain both monoecious and dioecious species.…”

The Cytology of Haplomitrium hookeri

“…I have already suggested (Berrie, 1958b) that the presence of two nucleolar organizers in Riccardia may be a character of phylogenetic significance. It is interesting to find this same character in a plant belonging to the Calobryales.…”