266 PROCEEDINGS OF THE AMERICAN ACADEMY 



long, and an inch distant from one another; spines 9-15 lines long. 

 Flowers 2 inches long, characterized by a very slender, constricted 

 tube, very diiTerent from the wide tube of the foregoing species. Seeds 

 fully Ig lines long, larger than those of any other Mamillaria examined 

 by me : embryo with some albumen, curved ; cotyledons foliaceous ! 

 approaching the structure of the seed of most Echinocacti. 



18. M. RECURVisPiNA, E. in B. C. R. : simplex, depresso-globosa ; 

 tuberculis ovatis profunde sulcatis confertis ; areolis obliquis ovatis, 

 aculeis radialibus 12 - 20 rigidis recurvis intertextis albidis corneisve, 

 aculeo centrali singulo (raro binis) robustiore longiore decurvato ; 

 floribus flavicantibus extus fuscatis ex axillis junioribus villosissimis. 



Sonora : fl. July. Single heads 3-8 inches in diameter ; tuber- 

 cles 5-6 lines long ; spines 4-9 Hues long, upper ones often a little 

 longer than the lower ones ; central spine 6-10 lines long, darker. 

 Flowers 1| inches long. — This plant bears the closest resemblance 

 to the next species, and must perhaps be classed with it ; but in the 

 dry specimen before me the flowers are not exactly vertical, as in that 

 species. 



* * DensiJlorcB. (Flowers and fruit remain central in the very 

 woolly vertex of the plant, no new tubercles being developed be- 

 fore the fruit falls ofi"; berries of all the species known to me oval, 

 green ; seeds brown, smooth.) 



19. M. coMPACTA, E. in Wisl. Rep. : simplex, depresso-globosa ; 

 tuberculis abbreviato-conicis sulcatis confertis ; areolis ovato-lanceo- 

 latis, aculeis radialibus 13-16 rigidis recurvis intertextis albidis cor- 

 neisve, aculeo centrali erecto plerumque deficiente ; floribus flavis 

 extus fuscatis minoribus. 



Cosiquiriachi, west of Chihuahua : fl. June and July. Plant 2-4 

 inches in diameter ; distinguished from the last species by the acutish 

 (not obtuse) tubercles, the more elongated areola, the erect central 

 spine, which however is wanting in most specimens, and principally 

 by the smaller and truly vertical flowers. Spines 5-10 lines long ; 

 flower 1;^- 1^ inches long and wide; seed 0.7 line long. 



20. M. PECTiNATA, E. in B. C. R. : simplex, globosa ; tuberculis 

 conicis abbreviatis, summis floriferis teretibus longioribus sulcatis ; are- 

 olis oblongis ; aculeis 16-24 rigidis recurvis intertextis suba^qualibus 

 s. in tuberculis summis superioribus longioribus fasciculatis omnibus 

 radiantibus cornels s. albidis ; floribus magnis sulphureis. 



On the Pecos River, in Western Texas : fl. July. — Plant 1-2 



