ILLUSTRATED STUDIES IN THE GENUS OPUNTIA — II. 95 



EXPLANATION OF PLATES. 



Plate 2. — Diagrams of Opuntia fruits, natural size. Outlines were pre- 

 pared in the field by bisecting the fruit in the median longitudinal plane. 

 The cut surface was then placed upon a piece of paper and a pencil tracing 

 made of it. This plate is prepared from tracings of these field sketches. 

 1, Opuntia subarmata; 2, 0. Allaird; 3, O. megacarpa; 4 and 7, O. congesta, 

 the first is the sterile form of the fruit; 5, O. gilvescens; 6, 0. Canada; 8, 0. 

 arizonica; 9, O. caerulescens; 10, 0. Dillei. 



Plate 3.— Above, Opuntia rufida from type locality near Presidio, Texas. 

 The plant is not quite normal on account of the main stem having been 

 injured. Below, a cultivated two-year-old plant from a cutting secured 

 near Torreon, Mexico. 



Plate 4.— Above, Opuntia tricolor, a two-year-old plant under cultiva- 

 tion from a single joint cutting. Below, 0. Dillei upon limestone ledges 

 in the Sacramento Mountains of New Mexico. 



Plate 5. — Opuntia Allairei, joints and fruit (see also plate 2), all of cur- 

 rent year's growth. 



Plate 6.— Above, Opuntia caerulescens, marked by the hat. Cultivated 

 four-year-old specimens. Below, 0. Canada. 



Plate 7.— Opuntia gilvescens. Plate 8. — Opunita congesta. Plate S. — 

 Opuntia texana. Plate 10. — Opuntia arizonica. 



Plate 11. — Opuntia subarmata upon calcareous soil of western Texas. 



Plate 12. — Above, Opuntia Allairei, one season's growth from single 

 joint cutting. A flower was produced on last growth of season. Below, 

 O. microdasys. Compare the habit in this figure, which is from a native 

 plant in the State of San Luis Potosi, Mexico, with that of O. rufida in 

 Plate 3. 



Plate 13. — Opuntia seeds, natural size. 1, Opuntia texana; 2, O. Canada; 

 3, 0. rufida; 4, 0. subarmata; 5, 0. congesta; 6, 0. gilvescens; 7, 0. Dillei; 8, 

 O. arizonica; 9, O. Allairei; 10, O.megacarpa; 11, O. echinocarpa (there are 

 forms of this species with smooth seeds); 12, 0. Canada (compare with fig. 

 2); 13, O. microdasys. 



