Echinocactus diguetii Weber, Bull. Mus. Hist. Nat. Paris 4: 100. 1898.
Plants very stout, usually 1 to 2 meters, but sometimes 3 and 4 meters, high, 6 to 8 dm. in diameter or more; ribs numerous, sometimes as many as 39, rather thin; areoles large, 1 to 1.5 cm. long, somewhat elliptic, approximate or on old plants coalescent; spines 6 to 8, yellow, subulate, 3 to 4 cm. long, slightly curved and a little spreading; flowers numerous, 3 to 3.5 cm. long; scales on ovary and flower-tube ovate, closely imbricate, thin on the margin and somewhat lacerate; inner perianth-segments red with yellow margins, oblong, 2 cm. long; filaments pink, numerous; tube of flower below stamens very short; style yellow; fruit scaly.
Type locality: Santa Catalina Island, off Lower California.
Distribution: Islands of the Gulf of California.
This species which is common on several of the islands in the Gulf of California is perhaps the largest of all the visnagas or barrel cacti. On Santa Catalina Island, especially, enormous individuals are to be found and here it is the most conspicuous plant. It seems to have no very definite habitat, growing both on the mountain sides among the large igneous rocks as well as along the old shell beaches. These plants have an enormous display of surface roots with only a few weak supporting ones and consequently large plants can easily be toppled over. Its spines are all very much alike.
Mr. Ivan M. Johnston, botanist of the California Academy of Sciences' Expedition to the Gulf of California, who explored all the islands in the Gulf in 1921, writes of the distribution of this species, as follows: "I found the distribution of Echinocactus diguetii to be peculiar; I saw it at the following disconnected points: Angel de la Guardia, Carmen, Coronado, Dansante, and San Diego Islands, It seems to skip hither and thither over the Gulf Islands without rhyme or reason."
Illustrations: Bull. Mus. Hist. Nat. Paris 4: 99. f. 1; Contr. U. S. Nat. Herb. 16: pl. 123 B; Journ. N. Y. Bot. Gard. 12: f. 47; Bull. Soc. Acclim. 52: 53. f. 12, as Echinocactus
Plate xi, figure 2, is from a photograph taken by Dr. Rose on Carmen Island, Gulf of California; plate xii, figure 3, shows the flower of a plant collected by Dr. Rose on Carmen Island in 1911.
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