866 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



in 1521, Clavigero states that improved varieties of tunas were carried to- 

 Baja California by the early missionaries. He reports also that the Cochimf 

 name for the fruit " is the single vowel a." 



Joints of the stems all terete, elongate or short, cylindric to globose. (Sub- 

 genus Ctlindropuntia.) 



Spines without sheaths VII. CLAVATAE, 



Spines with papery sheaths. 



Spines, at least some of them, solitary, sometimes several ; ultimate 



branches slender, rarely more than 1 cm. thick I. LEPTOCAUXES. 



Spines always more than one ; ultimate branches stouter. 



Ultimate branches not over 2 cm. thick U. THUBBEIIIANAK 



Ultimate branches 2 cm. thick or more. 



Fruit dry III. ECHINOCARPAE. 



Fruit fleshy. 



Tubercles of young joints scarcely longer than broad. 



IV. BIGELOVIANAE. 

 Tubercles distinctly longer than broad. 



Tubercles narrow, high, laterally flattened V. IMBRICATAE, 



Tubercles broad, low VI. FULGIDAE. 



Joints, at least some of them, flat or compressed. (Subgenus Platyopuntia.) 



Stems annual, very slender XXIV. CHAFEEYANAR 



Stems perennial, stout or slender. 



Flowers dioecious ; petals very narrow XXIII. STENOPETALAK 



Flowers perfect ; petals obovate to oblong. 

 Joints easily detached from the plants. 

 Joints very easily detached, little flattened ; plants mostly low and 



with small joints VIII. PUMILAE. 



Joints not so easily detached, flattened ; plants mostly taller and 



with larger joints IX. TUNAE. 



Joints not easily detached, persistent. 



Areoles small, 1 to 2 mm. in diameter, mostly close together, not ele- 

 vated X. BASrLARES 



Areoles larger, mostly distant. 



Spines, when present, brown or yellow (white in O. setispina). 

 Spines brown, at least at base or tip. 

 Plants bushy or depressed. 



Spines acicular XI. SETISPINAE. 



Spines subulate XII. PHAEACANTHAE. 



Plants tall, sometimes with a definite trunk. 



XIII. ELATIORES. 

 Spines yellow, at least partially so. 

 Epidermis glabrous. 

 Areoles close together, bearing long brown wool. 



XIV. SCHEERIANAE. 



Areoles distant, without long wool XV. DILLENIANAE. 



Epidermis, at least that of the ovary, pubescent. 



XVI. MACDOUGALIANAE. 

 Spines, when present, white (or faintly j'ellow). 

 Epidermis pubescent. 



Spines acicular XVII. TOMENTOSAE. 



Spines setaceous, flexible XVIII. LEUCOTRICHAE. 



