762 



POPULAR SCIENCE MONTHLY. 



of the Coliseum of Rome, consists conspicuously of fleshy-leaved 

 Sempervivums and Senecios, whose roots penetrate the tiles of the 

 houses and the stones of the streets. It is curious how many of these 

 fleshy plants have their leaves growing in rosettes, producing a simi- 



Opuntia tuna, the wild prickly pear witli bright scarlet fruils. 



larity between the members of widely separated orders (e. g., 

 Euphorbia halsamifera, Sonchus Kleinia, species of Sempervivum, 

 Senecio, and Statice). Is this also a means for the reduction of 

 transpiration? 



The same question (this time as regards the flowers) applies to 

 the species whose blossoms close soon after noon. The volcanic 

 wastes, brilliant in the morning with the bright flowers of Helian- 

 themum., Fagonia, Calendula, Sonchus, and Anagallis, are in the 

 afternoon like a house where the lights are gone out, for all the blos- 

 soms have gone to sleep, and there is nothing in sight but brown soil 

 and dull-green leaves. 



The curious plants with twiglike leaves seem also to have been 

 provided against too great loss by transpiration. Such are Plocama, 

 a strange rubiaceous shrub which looks like a diminutive weeping 

 willow; Genista rhodorhizoides, called by the insulars " retama," 

 whose flowers appear even in the dry season, and, in the time of rain, 

 whiten the hills; Spartium junceum, an even more perennial 

 bloomer, with brilliant yellow blossoms brightening dusty waysides; 



