18 



native home of the cacti may be reproduced with wonderful accuracy. 

 Winding paths may be laid out through the tract and the borders 

 planted in irregular groups, so that the effect will change as one 

 passes along any of the walks. 



Throughout the Southwest are to be found many very effective orna- 

 mental plantings of cacti, a very large proportion of which are vari- 

 ous species of Opuntia of either the flat- jointed or cylindrical forms. 

 These usually predominate, if not in variety certainly in quantity 

 of material, mainly owing to their rapidity of growth and ease of 

 propagation. A few collections are classic. Among the most noted 

 should be mentioned the one in the A. $. White Park at Kiverside, 

 Calif, (pi. 15, B) ; the Huntington collection at San Gabriel, Calif.; 

 the Letz collection at Hollywood, Calif. ; and the small but effective 

 university collection at Tucson, Ariz. ; all of which are unique park 

 examples. Whether for individual specimens or mass effect the 

 plants possess an individual charm which might be described as 

 grotesque by some, formal, stiff or delicate in coloration and blend 

 of tone, depending on the temperament and point of view of the 

 observer. 



One of the most pleasing plantings of cacti which have come under 

 the observation of the writers was the assemblage of Opuntia in the 

 United States Plant Introduction Garden at Chico, Calif., about 

 1915. (PL 17, A and B.) Close to 3,500 numbers of this genus had 

 been assembled here for study. They were planted from 4 to 9 feet 

 apart, depending on the stature of the plants. The setting was made 

 mainly for economic purposes, with no thought for ornamentation. 

 Still the varied forms were exceedingly attractive throughout the 

 year. A colored plate taken in the position of Plate IT, A, registered 

 11 distinct greens. This variation in color of plant body, coupled 

 with the varicolored fruit and the copious inflorescence, all of intense 

 interest and attractiveness, produced a very pleasing effect. 



PECULIARITIES OF CACTI 



To the lover of the unusual the cacti make a special appeal. Their 

 differences from all other plants suffice to put them in a unique group. 

 The Euphorbias of the African deserts simply simulate them in 

 general aspect, but really are not like them. 



Were one to define the group he could not do better than to say 

 they are plants having specialized structures called pulvini, cushions, 

 or areoles. (Fig. 1.) This definition sets them off from all other 

 groups of plants. They are exceedingly diverse succulent plants 

 whose vegetative portions are reduced to stems; whose leaves are 

 rudimentary and function but a few days, if at all ; whose buds are 

 modified into pulvini or cushions, found in no other family. The 

 cushions are usually not protuberances, like buds, but are actual 

 depressions on the surface of the plant filled or more properly built 

 up in a most complex way, often of three classes of spines, wool, 

 glands, growing points, etc. The spines of one large genus 

 (Opuntia) to which the prickly pears belong have retrorsely barbed 

 spines and spicules, (Fig. 2.) 



The cacti have lost their leaves and it may be said their branches 

 as well, the plant body being columnar, globular, simple, or branched. 

 Many of the species, especially of Opuntia, secrete nectar in their 



