408 HORTUS MORTOLENSIS 
Prof. Penzig,* of Genoa, where it is also grown in the open. 0. 
Pohlianum was received from Prof. R. von Wettstein in 1906, 
who had collected it in Brazil. The other Brazilian species came 
from the late M. Binot in 1904. 
OPUNTIA. 
Most Mexican species thrive exceedingly well at La Mortola ; 
those from the United States and the Andes succeed less, and 
evidently find our summer too dry. Opuntias in general are 
‘strong feeders,’ and enjoy good soil and plenty of water whilst 
growing. We have perfectly realized here what Mr. David 
Griffiths writes about them in Bulletin No. 60, p. 29 :— 
‘Prickly pear and other cacti are apparently inseparably | 
connected in the public mind with drought and heat, but this 
conception of the requirements for their best development is far 
from perfect. Our driest deserts produce none of these plants in 
economic quantities, and the same is true of our hottest regions. 
Rather than say they are adapted to conditions of extreme heat 
and drought, we should say that they thrive best in a region 
which has an equitable temperature, and a considerable rainfall 
periodically distributed. There is certainly no region in the world 
where these plants grow naturally in such profusion as they do 
upon the plateau of Mexico, but this is not a hot country, neither 
is it excessively dry. . . . it has a considerable rainfall . . . during 
summer, and then the country looks like anything but a desert.” 
The present large collection of Opuntias at La Mortola was 
begun by Mr. D. Hanbury. In later years almost every available 
form from European gardens has been tried here. Many of them 
still need identification. A large number of species were given us 
in 1901-4 by the late Dr. A. Weber, of Paris, including many 
type specimens. Others were received from Mrs. K. Brandegee, 
of Flagstaff, in California; from Prof. Arechavaleta, of Monte- 
video, Mr. D. Griffiths, of the United States Department of Agri- 
culture, Prof. Britton, of New York, from the late Mr. Hichlam, 
of Guatemala, from M. Puteaux, of Versailles, from Prof. Sohrens, 
Santiago de Chili, from Prof. Trabut, of Algiers, and from Mr. 
Winter, of Bordighera. A complete set of species collected in the 
United States by Mr. C. A. Purpus was sent by his brother, Mr. 
A. Purpus, from the Darmstadt Botanic Garden. 
The genus Opuntia is one of the most interesting of the 
Cactace@, being so rich in forms and varieties that it almost 
approaches Ffosa or Rubus. A careful monograph drawn up 
from living plants is urgently needed. From an economic point 
of view many species are greatly esteemed in their native land 
as fruit for man and as food for stock. In the United States 
Department of Agriculture. this question has been seriously 
studied by Messrs. D. Griffiths and R. F.. Hare, who have al- 
* Prof. O. Penzig states (Malpighia, viii. (1894), p. 464) that his plant came 
from the garden of an Italian gentleman at San Francesco d’Albano, where it 
was grown for more than thirty years on an orange tree in the open. 
eee rc errr. Cm 
