BEHAVIOR OP SPECIES OF CACTI. 7 



the past, it is believed, even led to the establishment of botanical 

 species upon such rudimentary conditions. 



ADAPTABILITY TO CONDITIONS. 



In a general way only can one classify these species with reference 

 to their adaptability to varying conditions, and the subject can only 

 be treated very briefly here. It would be necessary to list 300 or 

 400 species and tabulate the results obtained with them in our trials 

 before anything comprehensive could be deduced. This will be pos- 

 sible later, but a few observations of a general nature are desirable 

 here. 



The Arizona and New Mexico species in general make a fairly 

 normal growth at Chico, Cal., in spite of much greater fertility and 

 heavy winter precipitation. The color is a little modified in plant 

 body and spines, probably due to the long, dry summer. The growth 

 otherwise is quite normal. 



At San Antonio, Tex., these desert species put on a greatly in- 

 creased vegetative growth and produce fruit in moderate quantity. 

 Many species x have joints very much increased in size, comparable 

 with the " robusta " group at Brownsville, described below. . The 

 joints of these species are often fully twice as large at San Antonio 

 under cultivation as they are normally in their natural homes, and 

 many of them become less erect in habit. (PL III, fig. 2.) Of course, 

 we are discussing plants under cultivated conditions. This doubtless 

 accounts for some of the difference, but it is certain that the added 

 fertility and moisture influence much more. Under the still greater 

 humidity and fertility of the Brownsville region it is scarcely pos- 

 sible to grow these plants at all. They may start to grow, but 

 become exceedingly turgid, break down, and rot. Even the cylin- 

 drical forms 2 which grow so rampant at San Antonio make usually 

 only a slow, weak development, while the closely related species 3 

 which also grow normally under hard conditions do very well. How- 

 ever, much depends on the season, it being much more difficult to 

 handle the desert forms at Brownsville in wet than in dry years. 



A matter which has surprised the writer not a little is the be- 

 havior of the species of the Laredo (Tex.) district. This region is 

 not far removed from either San Antonio or Brownsville, it is true, 

 but the conditions are very different. The rainfall is less and even 

 more uncertain, and the fertility of the soil in the particular locali- 

 ties from which the plants were secured is much less than at either 

 San Antonio or Brownsville. In spite of this, many species 4 of 



1 Opuntia discata, 0. canada, O. toumeyi, and others. 



2 Opuntia versicolor and O. spinosior. 



3 Opuntia imoricata, O. prolifera, O. cardenche, and 0. pallida. 



4 Opuntia cacanapa, O. tricolor, forms of O. leptocaulis, and O. vexans. 



