6 CIRCTJLAB 



roots have been formed. When mature plants are shipped in from 

 the field the roots are always more or less injured. It is always best 

 to cut away the roots, let the wounds dry and heal for a time, and 

 then plant. 



Many of the opuntias are naturally adapted to vegetative propa- 

 gation. The stems are readily detached at the joints. These stems 

 fall to the ground and in a short time develop roots and begin to 

 grow as independent plants. Some are adapted for even wider 

 dissemination. The spines which they bear are very sharp, stiff, and 

 barbed. They penetrate the skins of passing animals and cling so 

 tenaciously that the joints bearing them are readily detached from 

 the parent plant and may be carried a considerable distance before 

 being released from their carrier. Once lodged in proper soil under 

 favorable climatic conditions, they soon become new individual 

 plants. In many of the opuntias the fruits are proliferous. They 

 may be removed and treated as cuttings and will readily produce 

 new plants. Many of the smaller forms, such as Echinocactus, 

 Echinocereus, and Mammillaria, produce branches (pi. 2, A and B), 

 which are readily detachable and are easily rooted as cuttings. Some 

 species of Mammillaria, as well as Opuntia, have side shoots or 

 branches which are so lightly attached that they break off by a slight 

 touch. Such plants depend almost entirely on vegetative propaga- 

 tion, and some of them rarely produce flowers and fruit. 



GRAFTING 



Grafting is easily accomplished throughout this whole group of 

 plants. The possibilities of uniting both species and genera seem to 

 be unlimited. For a long time it has been a practice to graft 

 Epiphyllum on Pereskia, or some upright, stiff-stemmed Cereus, in 

 order to produce a more decorative bushy plant. The rat-tail cactus 

 (Aporocdctus {Cereus) flayelliformis) is frequently treated in the 

 same manner. Aside from its ornamental possibilities, grafting 

 may be resorted to profitably as a means of propagation. It not 

 infrequently happens that a plant becomes decayed at its base, and 

 when all evidence of decay or disease has been removed there will be 

 so little healthy tissue left that it is next to impossible to get it to 

 grow as a cutting. Such a piece may be grafted on a healthy stock 

 and the plant be preserved if the growing tip is intact. A cleft 

 graft or a saddle graft is more desirable where either of these can be 

 employed,' since they require less work in preparation and give a 

 good large surface for the union of the tissues. The mucilaginous 

 sap that exudes from the cut surface of a cactus plant causes the stock 

 and scion to slip apart very easily, and the parts become disarranged 

 unless proper precaution is used to prevent it. For this purpose the 

 needlelike spines of Pereskia or Opuntia may be used. The two 

 parts are pressed firmly together into the desired position, and then 

 a spine is thrust through the united portions, securely pinning them 

 in that position. No wax is required, but it is best to closely wrap 

 the graft with raffia to exclude the air. The grafted plants are 

 then placed in a warm, moderately moist place until the tissues 

 have become thoroughly knitted together. They should not be 

 placed where they might be subject to drying, for under such con- 



