Cacti at HeJidon Vicaras.e. 



313 



opposite direction. By being brought together, they will now 

 be found to form diamond-shaped openings ; at the intersections a 

 small piece of bark must be removed from each stem, and the stems 

 bound together, and clayed in the same manner as for grafting : 

 as the trees grow, they can be inarched to the pendulous branches 

 of the weeping ash. This will be found to form a very strong 

 living arbour ; and by the same means a very strong and orna- 

 mental fence might be formed in a short time. 1 have no doubt 

 other trees will answer the same purpose, but the ash is the only 

 one I have seen tried. — AiJril 16. 1841. 



Art. VII. Catalogue of the Cacti in the Collection of the Rev. Theo- 

 dore Williams, at Hendon Vicarage, Middlesex. By George 

 Lawrence, Gardener there. 



Tribe PHYMATOCOTYLEDO^NEiE. 



Genus I. ANHALO NIUM. 



Syn. Arioca'rpus. 



Form globular, top nearly flat or level. Tubercles formed of thick fleshy 

 leaves (perhaps more like those of an aloe than a cactus) ; broad at the 

 base, tapering to an acute, unarmed, and naked point ; the upper side nearly 

 flat, and the under side keeled. Plant glaucous, with white down between 

 the tubercles. Flowers and fruit said to resemble those of Mammillaria. 



1 prismaticum. 2 in. high and 5 in. 

 in diameter, — Syn. Ariocarpus 

 retusa. 



2 p. 2 majus. 2 in. high, and 3 in. 

 in diameter. 



Genus II. MAMMILLA^RIA. 



Surface teated or tubercled. Flowers short, produced between the teats. 

 Berry long and pulpy, concealed in an envelope of down till the seed is 

 nearly matured, when it shoots forth, and presents itself to view. 



Sect. I. SETA^CEiE. 



Subsect. 1. LEUCOCE'PHALyE. — 



White-headed. 



1 geminispina. 4 in. high, and 6 in. 



in diameter; 3 heads. — Syn. 

 M. acanthophlegma ; M. leu- 

 cocephala ; Cactus columnaris. 



2 elegans. 3 in. high, and 5 in. in 



diameter ; 5 heads. 



3 polycantha. 4 in. high, and 4 in. 



in diameter. 



4 tetracantha. 5 in. high, and 3| in. 



in diameter. — Syn. M. super- 

 texta. 



5 Parkinsons. 3^ in. high, and 4 in. 



in diameter. 



6 lanifera. 4 in. high, and 2\ in. in 



diameter. — Syn, M. mona- 

 cantha. 



Species having bristles and spines. 



7 Perote. 3 in. high, and 3^ in. in 

 diameter. — Syn. M. diacantha 

 nigra; M. Haage«wa. 



8 sphaerotricha. 3 in. high, and 

 31 in. in diameter. — Syn. M. 

 Candida. 



9 semWs Lodd. Sin. high, and Sin. 

 in diameter. 



10 bicolor. 2i in. high, and 2 in. in 

 diameter. — Syn. M. gemini- 

 spina ; M. nivea var. minor. 



lib. var. monstrosa. 4 in. high, and 

 9 in. in diameter. — Syn. M. 

 b. serpentina. 



12 nivea. 5\n. high, and 16 in. in 

 diameter; 35 heads. — Syn. 

 M. Toaldoo?. 



IS rosea. 2^ in. high, and 4 in. in 

 diameter ; S heads. 



