LEtrOHIENBEEGIA. 



29 



Helwingia and Erythrochiton. Lemaire partly adopted thia 7iew 

 regarding the mammae of the three genera Mamillaria, Pelecyphora, and 

 Leuchtenbergia as metamorphosed leaves, the spines representing the 

 veins of the leaves, in which opinion many careful observers agree. Le 

 Maout and Decaisne describe them as " arrested buds," and would thus 

 give them more the nature of branches, while others incline to the view 

 that they are simple elevations of the substance of the stem similar to 

 the ridges in Echinocactus and Oereus. 



This is a rather difficult plant to grow satisfactorily, but it should be 

 treated similarly to the Mamillarias as regards soil, and most carefully 



Fig. 5. — Leuchtenbergia principis (reduced). 



attended in the supply of water, as the slightest approach to excess will 

 result in serious injury and probably the death of the plant, 



Leuchtenbeesia pniNCiPis, HooJcer. — In 18i8 au excellent figure of this 

 plant was given in the " Botanical Magazine," accompanied by a full descrip- 

 tion by Sir W. Hooker, which is so graphic that it is here reproduced. " Our 

 largest plant is a foot high, its main trunk erect, but crooked, as thick as a 

 man's arm, clothed with the dense mass of persistent bases of old mamillse, or 

 perhaps rather of the withered mamillse themselves, shrunk and reduced to a 

 mass of closely pressed scales. Above they gradually become more perfect, 

 at first short and truncated till the crown of the plant is clothed with per- 



