S.M. Bukasov. Potatoes of South America and their breeding use, Leningrad, 1933, p. 78
Diagnosis: Distincts from f. chalcoense in longer calyx acumens, about 4 mm long, which equals to 1/3-1/2 of the whole calyx length, longer pubescence, and light-yellow anthers, the earliest flowering from the whole variety.
Auricles of the flower stalk are sometimes splitted. Flower-bearing leaf of the second tire is more dissected, than by the first one. Its formula is 2/4 2,4+2,4, i.t. four couples of leaflets (numerator), two out of them (denomenator) are smaller; in the end series there are two primary leaflets (the first number), in the second 4+ two secondary leaflets, in the thire 4 primary leaflets.
Apex leaves can be like by tolucanum. More than one tire of inflorescences. Pedicel below articulation is 22 mm long, above articulation 7-8 mm long, long thin pubescence, staring. Calyx is up to 12 mm long, with narrow acumens. Stamen filaments are thin (650) 740-830 (940) micr. Anther size is 6Õ2-2,2 mm, their column is slightly conic.
Style is 8 mm long, 510-630 µ thick, slightly exserted over the stamens. Papillae are usually longer than by tolucanum, 53-72 micr. Stigma has a diameter up to 2/64 inches, slightly flattened, with a big sinus. Sexual progeny reproduces the original form with insignificant variations.
Republic of Guatemala: Quetzaltenango (¹¹9,10), San Felipe (¹12), Amatitlan (¹¹13 and 15), Escuintla (from Quetzaltenango (¹16).
Accessions are collected by Vavilov in Mutla (1669 m), state Oaxaca, also referred to v. Mexicanum by tubers.
Accessions bought by W.M. Benzin on the market in Mojolo (state Tamaulipas), refer to the same variety as wild. Apparently, they are a mixture of f. chalcotnse and f. tolucanum. Strong affection to late blight did not allow them to flourish.