12 BULLETIN 31, U. S. DEPARTMENT OF AGRICULTURE. 



At San Antonio the group is not hardy, but a few protected plants 

 are about midway in their behavior between those at Chico and at 

 Brownsville. A couple of plants 5 years of age are 11 feet high, 

 with no sign of blossoming yet. The vegetative growth here is 

 heavy during the summer, but always interrupted by the severe 

 cold of winter, the plants usually being killed outright, but some- 

 times only to the ground. 



The effect of excessive moisture on a few species is very striking. 

 It is a common experience to find fruits ruptured by excessive tur- 

 gidity at maturity, and at times stems are found in the same condi- 

 tion. Under excessive moisture, or an abundance of the same, joints 

 are always turgid. In rare instances where excessive pruning has 

 been practiced the vascular system of the joints is actually so modi- 

 fied as to change it from the normally flat form into a lenticular 

 outline, the same becoming twice its normal thickness and the tissues 

 tremendously distended. Such a phenomenon has been observed 

 under the conditions mentioned in Opuntia pachona* O. decumbens, 

 and an unnamed species from Aguascalientes, Mexico, grown at 

 Brownsville. This phenomenon, however, is rare, and probably is 

 a forerunner of a pathological condition. 



One group of cylindrical- jointed species 1 are fragile jointed natu- 

 rally, and all produce some small few-spined joints in their natural 

 state, but this character is very much accentuated under the Browns- 

 ville conditions. In spite of the favorable conditions and the rapid- 

 ity of growth, it takes them longer to reach the normal adult form 

 here than in their natural habitat. None of these species, however, 

 grow perfectly at any of our stations. 



EFFECT OF HOUSING. 



Succinctly stated, the housing of these plants under glass, with 

 either little or no heat or with a temperature kept at a point not 

 lower than 40° F. by the use of artificial heat, tends to stimulate vege- 

 tative growth at the expense of fruit production. This, of course, in 

 a general way would be expected. 



In order to fruit out a number of Mexican species of doubtful frost 

 resistance two years ago. duplicate plantings were made at Chico 

 under glass and in the regular field plantation. Fortunately none of 

 these species, of which there were nearly 100, failed to live through 

 the winter of 1911-12 on account of cold. They were all seedlings set 

 in the spring of 1911 from the nursery row. being then one and one- 

 half years from seed. The third year about 20 of this lot fruited to 

 some extent in the field. The plants in the house made at least three 

 times the growth, but none of them fruited. The difference is very 



1 Opuntia tunicata, 0. i><(lli<in, O. fulgida, and 0. mamillata. 



