CHAP. V. ORNAMENTAL TREES, SHRUBS, ETC. 573 



richest possible soil, but at the same time it must be capable of 

 admitting the water to pass through it freely, and for that reason 

 may have a portion of lime-rubbish, broken pots, or small pieces of 

 broken bricks mixed with it, to keep it open and porous. Poor 

 sandy soil should be discarded, and even peat earth is not rich 

 enough for these plants." * 



They are very tenacious of life ; a single joint may be con- 

 veyed almost any distance without detriment, and will strike 

 upon being inserted in sand and kept moderately watered. In 

 England those of a spheroidal form are sometimes grafted upon 

 stocks of Pereskia aculeata, by making a small hole in their 

 base and placing it upon the stem of the Pereskia, sharpened to 

 a point, and binding a little moss round the place of juncture of 

 graft and stock. 



Melocactus. 

 TURK'S-CAP, OR MELON-SHAPED CACTUS. 



A name significant of the form of the plants, which produce 

 their flowers on a head covered with dense woolly and bristly 

 hairs. M. erectus is in the Botanical Gardens. Others noted 

 as most worthy of cultivation are : M. depressus ; Grengelii ; 

 macracanthus ; polycanthus ; pyramidalis ; Sellowii. 



Mammillaria. 



NIPPLE-CACTUS. 



Described as "dwarf plants composed of an assemblage of 

 tubercles, somewhat resembling the teats of animals. These are 

 generally terminated with bunches of hairy bristles, and between 

 them the flowers appear." f To me they rather look like, as 

 regards form, a cluster of small Gherkins. The few that our 

 gardens contain, so far as I am aware of, are : 



1. M. tennis. Pretty and delicate-looking from its club-like 

 lobes being hoary with bristles. Suited to a pot of about the 

 size of a tea-cup. Flowers described as pale yellow. 



2. M. pusilla. Kesembles a little heap of balls of worsted ; 

 flowers described as pale red. 



3. M. longimamma. Lobes or tubercles long and thin, like a 



* 'The Greenhouse,' pp. 182 and 186. f 'Cottage Gardener's Dictionary.' 



