Monographs Details:
Authority:
Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
Family:
Cyperaceae
Cyperaceae
Description:
Species Description - Judging from the many names referable to the Becquerelia cymosa complex, previous authors realized that there was a taxon closely allied to but differing from B. cymosa. Detailed study on variations in the complex has convinced me that the achene dimensions are of significance in distinguishing the taxa in this complex. One mature achene from each of over 100 collections from the total distribution range was measured and then plotted in a scatter diagram (Fig. 8). As far as the achene size is concerned, it can be seen from the diagram that there are two groupings in the complex. The scatter diagram shows an obvious bimodal distribution of measurements. In this connection, the name Becquerelia cymosa represents the plant with large achenes generally more than 2.5 mm in diameter, whereas the name B. merkeliana is attributed to the plant with smaller achenes less than 2 mm across. The segregation primarily made by the achene dimension is supported by the character of inflorescences and the size of glumes. In B. cymosa the interrupted inflorescences are loose with usually less than 10 branchlets each with 3 to 5 secondary ranchlets, whereas in B. merkeliana the contiguous inflorescences are dense with 10 to 15 branchlets each with up to 8 secondary branchlets. The glumes of large-fruited B. cymosa are larger than those of small-fruited B. merkeliana by 3 to 3.5 mm vs 2.5-3 mm in the length of mature glumes. Intermediate states were seen also in these additional characters.
Species Description - Judging from the many names referable to the Becquerelia cymosa complex, previous authors realized that there was a taxon closely allied to but differing from B. cymosa. Detailed study on variations in the complex has convinced me that the achene dimensions are of significance in distinguishing the taxa in this complex. One mature achene from each of over 100 collections from the total distribution range was measured and then plotted in a scatter diagram (Fig. 8). As far as the achene size is concerned, it can be seen from the diagram that there are two groupings in the complex. The scatter diagram shows an obvious bimodal distribution of measurements. In this connection, the name Becquerelia cymosa represents the plant with large achenes generally more than 2.5 mm in diameter, whereas the name B. merkeliana is attributed to the plant with smaller achenes less than 2 mm across. The segregation primarily made by the achene dimension is supported by the character of inflorescences and the size of glumes. In B. cymosa the interrupted inflorescences are loose with usually less than 10 branchlets each with 3 to 5 secondary ranchlets, whereas in B. merkeliana the contiguous inflorescences are dense with 10 to 15 branchlets each with up to 8 secondary branchlets. The glumes of large-fruited B. cymosa are larger than those of small-fruited B. merkeliana by 3 to 3.5 mm vs 2.5-3 mm in the length of mature glumes. Intermediate states were seen also in these additional characters.
Discussion:
From the above morphological evidence the small-fruited B. merktliana m ay be regarded as a subspecies of B. cymosa. The two subsptcie> thus separated, i.e., subsp cymosa and subs]-) merkeliana, are not phytogeographically distinct. The range of subsp merkeliana, which is confined to the Amazonian basin, the Guianas, and eastern Brazil, is completely included within the range of subsp cymosa covering the entire Guayana, the lowland Guianas, Amazonas, northern Andes, and Trinidad.