Taxon, 1(8): 121-123 (Nov 1952)
Biosystematic experiments involving Zephyranthes, Habranthus and Amaryllis
by HAMILTON P. TRAUB
(Beltsville, Md.)

Within the Amaryllidaceae the genera Zephyranthes Herb., and Habranthus Herb., are assigned to the Tribe Zephyrantheae on the basis of a number of characters including the spathe which is tubular below for part of its length in contrast with the genus Amaryllis Linn. with spathe-valves 2, free to the base, which has been placed in the Tribe Amarylleae. In a recent monograph of the Tribe Amarylleae (TRAUB & MOLDENKE, 1949) it was found desirable to subdivide the species of the genus Amaryllis Linn. into two un-named supra-groups of taxons, — (a) the narrow-leaved, small-flowered species (hereinafter referred to as the "narrow-leaved supra-group"), and (b) the broaderleaved, larger-flowered species (hereinafter referred to as the 'broader-leaved supra-group").

Within the genus Amaryllis Linn., gene exchange was demonstrated over a century and a half ago in the broader-leaved supra-group beginning with X Amaryllis johnsonii Johnson ex Herb. (Amaryllis reginae Linn. X Amaryllis vittata L'Hérit.). The basic chromosome number in this supra-group is x = 11, and the chromosome series includes 2n = 22, 44 and 77 (see Summary in TRAUB & MOLDENKE, 1949). All attempts to cross species of the narrow-leaved supra-group with those of the broader-leaved supra-group have uniformly failed. FICKER (1951) reported chromosome studies of two species of the narrow-leaved supra-group, Amaryllis bifida (Herb.) Sprengel and Amaryllis chilensis L'Hérit., in both cases the diploid chromosome complement is 2n = 18, and the basic chromosome complement of the supra-group, on the basis of this report, is x = 9. This difference in chromosome complements might explain the failure to obtain hybrid progeny between species of these two supra-groups.

Recently, the present writer has obtained a cross between Amaryllis bifida (Herb.) Sprengel and Amaryllis chilensis L'Hérit., two species in the narrow-leaved supra-group. A detailed report on this work will appear elsewhere.

On the basis of our present knowledge, apparently, the narrow-leaved supra-group is not closely related to the broader-leaved supra-group within the genus Amaryllis Linn. This seems to be confirmed on the basis of another series of experiments which are briefly summarized in Table 1, and the text. A more detailed report will appear elsewhere.

The present writer suspected that the species of the narrow-leaved supra-group were closely related to the species of the genus Habranthus Herb., and he therefore tested that hypothesis, and obtained reciprocal crosses between Amaryllis bifida (Herb.) Sprengel and Habranthus juncifolius Traub. The progeny have bloomed and are intermediate between the parents in most characters. All have proved to he self-sterile so far. FLORY (1948) showed that the chromosome complement of Habranthus juncifolius Traub is 2n = 14.

In another experiment, Habranthus juncifolius Traub was crossed on Zephyranthes grandiflora Lindl., which has a chromosome complement of 2n = 48. The progeny thus received a larger proportion of chromosomes from the latter species, and show the influence of that species in a larger measure than that of Habranthus juncifolius Traub. The leaves, the spathe of which is tubular below, and the usually radially-symmetrical perigone are similar to those of Zephyranthes grandiflora Lindl., but the androecium and gynoecium are bilaterally symmetrical and similar to those of Habranthus juncifolius Traub — the stamens and style are definitely declinate, the stamens are much shorter than the style and show a tendency toward the fasciculate grouping. So far all have proved to be self-sterile. Chromosome studies of these progeny will be reported elsewhere later.

The implications of these results are obvious. It is clear that either the Tribe Zephyrantheae should be merged with the Tribe Amarylleae, or the narrow-leaved supra-group of Amaryllis Linn., under the name Rhodophiala Presl, which has priority under the International Code, should be transferred to the Tribe Zephyrantheae. No final decision on this matter has been reached. At any rate, the genus Rhodophiala Presl has to be restored with Rhodophiala amarylloides Presl as the type ( = Rhodophiala pratensis (Poeppig) Traub, comb. nov., syn. — Amaryllis pratensis Poeppig, in Fragm. Syn. Pl. Phan. 5. 1833).

TABLE 1.
Summary of biosystematic experiments involving Zephyranthes Herb., Habranthus Herb., and Amaryllis Linn.
("X" indicates that a successful cross was made as shown by living progeny.)

Tribe Zephyrantheae   Tribe Amarylleae
Zephyranthes
Mostly radial floral symmetry1)
  Habranthus
Bilateral floral symmetry
  Amaryllis Linn.
(Narrow-leaved supra-group)
Bilateral floral symmetry
        Amaryllis bifida 
(Herb.) Spreng.
(2n = 18)
X Amaryllis chilensis
L'Hérit.
(2n = 18)
    Habranthus  juncifolius
Traub (2n = 14)
X Ditto    
Zephyranthes  grandiflora
Lindl.2) (2n = 48)
X Ditto        
1) Style may be straight or more or less declinate.
2) Style somewhat longer than stamens and somewhat declinate.

The residual or broader-leaved supra-group of the genus Amaryllis Linn., thus becomes a very homogeneous taxon, with 36 species remaining of those admitted before 1949 (TRAUB & MOLDENKE, 1949) and with seven additions proposed since 1949 — Amaryllis ferreyrae  Traub (1950), Peru; Amaryllis fosteri Traub (1951), Brasil; Amaryllis espiritensis Traub (1951), Brasil; Amaryllis vanleestenii Traub (1951), Surinam; Amaryllis viridorchida Traub (1951), Brasil; Amaryllis oconequensis Traub (1951), Peru; Amaryllis maracasa Traub (1952), Brasil. In addition three undescribed species have been determined as new to science, one from Peru and two from Brasil, and will be proposed in 1952 and 1953.