140 PLANT WORLD. 



upper mamilla.'. The species is popularly known as "vaca" 

 (Cow-cactus) and is eaten raw, it serving to allay the thirst. 



In the species of Ecliinocacliis (E. pringelci Rose, Cac. 

 N. Zac, No. 13) known here as "biznaga colorada" nectar 

 glands occur just above the pulvini as three conical protub- 

 erances of yellow or orange color, about 5 mm. long, and 

 arranged in an obtuse triangle with the apex directed up- 

 ward. The extruding nectar appears first as a minute droplet 

 on the apex of the cone-shaped gland, and in the field the 

 glands are often found coated with a crystalline mass derived 

 from the evaporated fluid. 



Two other, as yet undetermined, species of Echinocactiis 

 (Nos. 10 and 33) have also been found to possess nectaries. 

 In the former species, No. 10, they have the same form as 

 in Echinocactiis priugJci Rose, but are more numerous, 

 arising in acropetal order, new ones being formed as the 

 older ones die. No. 33 has apparently only one nectar gland, 

 just above the pulvinus, and expanded transversely as regards 



the ridge. 



In Opinitia imbricata, No. 21, the nectar glands are 

 two in number on each pulvinus, so far as I have been able 

 to determine them up to the present moment. They are 

 placed just within the first pair of lateral spines formed, 

 and are readily seen in the young branches as small pale 

 green areas unclothed with hairs such as render the pulvinus 

 apparent. The amount of nectar formed in this species from 

 any one gland is not very great, but apparently there is 

 enough to attract many ants. 



In view of the number of species in which nectar glands 

 have been found by me, it seems probable that these struc- 

 tures are widely distributed in the family. 



Mazapil, Zac, Mcx. 



