EXPLANATION OF PLATES. 
Remarks.—All the figures are in natural size unless otherwise stated. The seeds of Mamil- 
lari, Echinocacti, and Cerei are represented in the natural size, and eight times magnified: a 
is a lateral view, natural size; b, same, eight times magnified ; ¢, part of the surface of the seed 
still more magnified ; d, seed after the removal of the outer coat, with endopleura and albumen ; 
e, embryo ; f, another form of same seed ; g, seedling plant; h, back view ; ¢, front view; &, 
basal view ; 7, top view of embryo—all eight times magnified. 
The seeds of Opuntiz, being larger, are represented: a, side view, natural size ; b, same, four 
times magnified, as are all the following ones; ¢, posterior view; d, anterior view; e, vertical 
section ; /, seed after the removal of the testa ; g, embryo. 
The landscape opposite the title-page represents a region near the Colorado river, with several 
Cacti, especially Cereus giganteus; one of them decayed, showing the form of the ligneous 
skeleton. The different plants are accurate copies of nature. 
Pu. 1. MAMILLARIA MICROMERIS: 1, a young plant not yet blooming, without the tuft; 2, a 
plant in bloom, with the tuft; 3 and 4, different views of a plant of the largest size; several 
fruits are seen in the tuft; 5, a tubercle with a bunch of spines, eight times magnified; 6, a 
bunch of spines in natural size, and 7 the same, eight times enlarged. 
Pu. 2. The same: 1, lateral view of a bunch of spines, and its wool on the flower-bearing part 
of the plant, eight times magnified, exhibiting the upper elongated clavate spines ; 2, flower, 
four times enlarged ; 3, fruit; 4, seed. 
Fie. 5-8. MaMItLaRTA MICROMERIS var. Greeeit: 5, bunch of spines; 6, same, eight times 
magnified, showing the ragged ends of the long spines where they are broken off; 7, a bunch of 
spines, with its wool from the flowering part of the plant, with the long clavate spines, eight 
times magnified ; 8, seed. 
Pi. 3. MAMILLARIA LASIACANTHA: 1, a plant of the ordinary size in flower; 2, flower, four 
times magnified ; 3, a tubercle with a bunch of spines, showing the pubescence, eight times 
magnified ; 4-5, bunches of spines, natural size, and eight times magnified. 
Pi. 4. MAMILLARIA LASIACANTHA var. DENUDATA: 1, a fruit-bearing plant; 2, a tubercle, with 
its bunch of spines, eight times magnified ; 3-4, bunches of spines, in natural size, and the 
same eight times magnified ; 5, seed. 
Pi. 5. Mamiiarta pusttta var. Texana: 1, whole plant in flower; 2, a tubercle, with a 
bunch of spines and the axillary wool, twice magnified ; 3, a bunch of spines, same; 4, flower, 
same ; 5, fruit natural size; 6, seed. 
