CHROMOSOME COUNTS IN CHEILANTHES AND ASPIDOTIS WITH A CONSPECTUS OF THE CYTOLOGY OF THE SINOPTERIDACEAE

Confirmatory, corrective and new chromosome counts are listed for species in the genus Cheilanthes, and a new chromosome count is given for a member of the genus Aspidotis. An analysis of five collections of C. castanea revealed no significant morphological differences despite the different chromosome numbers. The ploidy level of all known species in genera of the Sinopteridaceae is summarized, revealing directions in which future research might proceed to complete our cytological knowledge of this family. OF 12,000 SPECIES of living pteridophytes, chromosome number is known for only 1800 or about 15 % (Walker, 1973). Chromosome counting serves to increase the fund of human knowledge, and in some cases, it has aided us in deducing relationships. The morphological separation of genera is sometimes reinforced by the chromosome number, e.g., Athyrium x = 40, Diplazium x = 41, and Cystopteris x = 42. In other cases, unfortunately, genera may have the same number, e.g., Dryopteris, Polystichum, and Arachniodes, all of which have x = 41, as does Diplazium. Aspleniaceae has, with two exceptions, x = 36, but this same number is also shared with some members of Polypodiaceae and Thelypteridaceae (Lovis, 1973). There are more than 125 taxa of Cheilanthes, and chromosome counts have been made for 59. In Aspidotis (4-5 species; Lellinger, 1968), counts are known for four American taxa. In this paper we add six new counts plus some confirmations and corrections to Cheilanthes and one new count to Aspidotis, all of which are included in the totals for the 59 and the four taxa above. All new and corrected counts are recorded in Table 1. The addition of these counts and their comparison with those previously reported in these two genera, as well as with counts in related genera, should take us a step further in our understanding of chromosomal relationships of these groups. MATERIALS AND METHODS-The taxa used in this study are as follows: Cheilanthes aemula Maxon, Nuevo Leon, Mexico, Knobloch 2037 A; C. alabamensis (Buckl.) Kunze, Nuevo Leon, Mexico, Knobloch 2029 B; C. castanea Maxon, nr. Ironto, Va. Knobloch 1953; C. castanea I Received for publication 8 July 1974. 2 Present address: Roswell Park Memorial Institute, Springville, New York. Maxon, Davis Mts. Texas, B. Warnock s.n., accessions 63-28, 63-30; C. castanea Maxon, Carlsbad Caverns National Park, N. Mexico, J. K. Baker, s.n., accession 63-49D; C. chipinquensis Knobloch and Lellinger, Nuevo Leon, Mexico, Knobloch 1996 B; C. cucullans Fee, Oaxaca, Mexico, Knobloch 2457; C. eatonii Baker, Carlsbad Caverns National Park, N. Mexico, J. K. Baker s.n., accession 63-49B; C. feei Moore, Franklin Mts. Texas, Knobloch 1694 B; C. myriophylla Desv., Morelos, Mexico Knobloch 2222; C. notholaenoides (Desv.) Maxon ex Weatherby, nr. Jacala, Mexico. Lefebure 1284, acc. number 63-51; C. pulchella Bory ex Willd., Las Raices, Canary Islands, Mrs. W. A. Kenzie s.n., acc. 70-5; C. pyramidalis Fee, Durango, Mexico, Knobloch 2127; C. tomentosa Link, Tamaulipas, Mexico, Knobloch 2252; Aspidotis meifolia (D.C. Eaton in Wats.) Pic-Ser., Tamaulipas, Mexico, Knobloch 2251. Acetocarmine was employed in the squash method. Root tip preparations differed from spore mother cell preparations in that they were immersed in paradichlorobenzene for four or more hr and, after fixing in Carnoy's fluid, were hydrolyzed in 1 N HCL until the tips were soft. Photographs are provided for new or revised numbers. RESULTS AND DISCUSSION-Cheilanthes: Confirmatory counts were made for C. castanea from Ironto, Virginia, which has ca. 87 chromosomes in root tip cells (Knobloch and Lellinger, 1969a). Whittier's studies (1965, 1970) have shown this particular taxon to be apogamous. Prior to 1969 (Knobloch and Lellinger) the specimens from Ironto were thought to be C. tomentosa. Lloyd's count (1966) for C. eatonii (2n = 87); Knobloch's (1967) and Whittier's (1970) counts for C. feei (2n = 87); Knobloch's (1966, 1967) and Whittier's (1970) counts for C. tomentosa (2n 90) are also confirmed. These three plus