EXTKA-FI.OKAL NKC r.\Kli:S. I 39 



My attention was first drawn to the extra-floral secre- 

 tion of nectar in these plants in the case of a Mamillaria 

 (Cacti of N. Zac, Mex., No. 31*) with large mamihe. 

 The upper surface of the mamilla is grooved broadly, 

 the groove being lined with a thick felt of hairs. In this 

 groove occur the nectar glands, the largest of which lies 

 near the puKinus, and is dull orange in color. The exposed 

 surface is slightly convex. When the plant is thoroughly 

 washed to remove all the nectar from the exterior of the 

 surface, and placed in the sunlight, the whole becomes 

 thoroughly dried, except, probably, the felt of hair which is 

 found not only on the grooves but about the apex of the plant 

 as well. In about three hours the extrusion of a perfectly 

 limpid fluid from the center of each gland becomes evident, 

 and in the course of a day every active gland will have s 

 good sized, clear drop of nectar standing up from the 

 centers of the glands. It appears that the presence of water 

 in contact with the outer surface of the glands is not 

 necessary, though it was suspected that moisture in the felt 

 of hairs adjacent to the glands might help to start the secre- 

 tion, or rather the extrusion. In the plant studied almost all 

 the mamilhe secreted nectar, the largest drops occurring on 

 the younger mamills. The nectar quickly becomes very 

 syrupy, and often the sugar will become granular so that 

 the nectar may be broken away from the gland. Such an 

 amount of nectar is produced that it often runs into the 

 felt and renders the whole groove-covering sticky and mat- 

 ted with the syrup. 



Similar glands occur also in a species of Echinocactus 



(Cacti of N. Zac, Mex., No. 2) in which their distribution 



and appearance is similar to those in the species of Mamillaria 



just discussed. The rate of secretion appears, howe\'er, to 



be more rapid than in the latter, though it is confined to the 



*The plants here referred to are ilesigniitod by my collection numbers, the 

 specimens having been deposited in the U. S. National Herbarium. 



