Cytological and Phylogenetic Studies in the Cucurbitaceae

Abstract

1. The chromosome numbers of 12 species of the Cucurbitaceae have been determined from pollen mother cell material. The results may be summarized as follows: Melothria punctata, n = 12; Melothria abyssinica, n = 12; Momordica balsamina, n = 11; Luffa cylindrica, n = 13; Ecballium elaterium, n = 12; Citrullus colocynthis, n = 11; Cucumis myriocarpus, n = 12; Cucumis melo var. Golden Beauty, n = 12; Benincasa cerifera, n = 12; Cucurbita melanosperma, n = 20; Cucurbita pepo var. Orange gourd, n = 20; Cyclanthera pedata, n = 16. 2. The results of an experimental study of the fertility relations involving 4 genera and 8 species of the Cucurbitaceae indicate that species crossing is comparatively rare and not at all in accord with popular beliefs. Three species crosses were obtained: (1) between Cucurbita moschata and C. maxima; (2) between Cucurbita pepo and C. moschata; and (3) between Citrullus vulgaris and C. colocynthis. 3. The technique of making controlled pollinations among members of this family has been described. 4. The pertinent points in regard to chromosome number and geographical distribution are: (a) the Old World genera, with one exception, have basic numbers of 11-13; (b) there is a New World group having 16 as the basic number; and (c) there is a second New World group having 20-24 as the basic number.