ECHINOCACTUS. 
167 
about a dozen species of this relationship which have been described; to these we append 
3 species of the southwestern United States and border states of northern Mexico, one 
with smooth, the others with papillose seeds. 
Echinocactus texensis has a similar woolly ovary, but the fruit is fleshy, with different 
seeds and purple flowers; this we regard as a new generic type. 
Astrophytum with its 4 species, usually classed as Echinocactus, also has pubescent 
fruit, but is very different in other respects. 
There are 2 other cacti from North America which bear wool on the ovary, E. whipplei 
and E. polyancistrus . These have only small scales on the ovary, bearing minute tufts of 
hairs in their axils and have very different seeds. We refer them to a new genus (see p. 
212). 
In South America there are 2 old genera with woolly fruit which have been associated 
with Echinocactus, namely, Malacocarpus and Eriosyce, both of which, in our opinion, are 
generically distinct. 
Key to Species. 
A. Plants very large, often becoming cylindric (see No. 5). 
Spines all bright yellow. 1. E. grusonii 
Spines brown to gray, rarely some of them yellowish. 
Inner perianth-segments linear-oblong, entire . 2. E. ingens 
Inner perianth-segments oblong, more or less toothed or lacerate. 
Spines all of one kind. 3. E. visnaga 
Spines both radial and central. 
Central spine solitary. 
Flowers 4 to 5 cm. long; central spine 4 to 5 cm. long, nearly black. 4. E. grandis 
Flowers 3 cm. long; central spine 3 cm. long, grayish in age. 5. E. platyacanthus 
Central spines several. 6. E. palmeri 
AA. Plants relatively small, subglobose. 
Seeds smooth and shining. 7. E. xeranthemoides 
Seeds papillose. 
Flowers yellow. 8. E. polycephalus 
Flowers pink. 9. E. horizonthalonius 
1 . Echinocactus grusonii Hildmann, Monatsschr. Kakteenk. 1:4. 1891. 
Plants single, depressed-globose, large, 2 to 13 dm. high or more, often 4 to 8 dm. in diameter, 
light green; ribs 21 to 37, rather thin and high; spines when young golden yellow, becoming pale and 
nearly white, but in age dirty brown; radial spines 8 to 10, subulate, 3 cm. long; central spines usually 
4, up to 5 cm. long; flowers 4 to 6 cm. long, opening in bright sunlight, 5 cm. broad at top, the seg¬ 
ments never widely spreading; flower-tube 3 cm. broad, covered with lanceolate, long-acuminate 
scales; outer perianth-segments long-acuminate, brownish on the outside, yellowish within; inner 
perianth-segments cadmium-yellow, with a silky luster, erect, narrowly lanceolate, acuminate, much 
shorter than the outer segments; stamens numerous, yellow, connivent, forming a thick cylinder in 
the center of the perianth; style yellow; stigma-lobes 12; ovary spherical, bearing acuminate scales 
with an abundance of wool in their axils; fruit oblong to spherical, 12 to 20 mm. long, thin-walled, 
covered with white wool or becoming naked below; seeds smooth, dark chestnut-brown, shining, 
1.5 mm. long. 
Type locality: Central Mexico. 
Distribution: San Luis Potosi to Hidalgo, Mexico. 
This is a very attractive species and is much grown in collections, but usually only small 
plants are seen. 
We are greatly indebted to Mr. E. C. Rost, a private grower of cacti in southern Cali¬ 
fornia and a very keen observer, not only for procuring for us flowers, fruits, and good 
photographs, but also for valuable observations. He writes that the flowers are deeply 
imbedded in the dense felt cushion and must actually be dug out. The depth to which the 
flowers are sunk is shown by a definite band near the top of the ovary. The flowers open 
in sun-light and the perianth-segments are nearly erect or slightly spreading. The stamens 
and style are erect. Under date of October 9, 1919, Mr. Rost sent us the following state¬ 
ment regarding this plant: 
