ECHINOCACTUS. 1 67 



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. 



Eckinocactus 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. 



Astro phylum with its 4 species, usually classed as Eckinocactus, 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 Eckinocactus, 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. palmer i 



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: 



