Makoh 24, 1911] 



SCIENCE 



471 



Before the conquest of Mexico the Aztecs usea 

 certain spices and aromatic plants in confection- 

 ing their celebrated chocolate. The mostly highly 

 prized . by the ancient Mexicans was the flower 

 called teonacaztli, or xochinacastli ("sacred-ear" 

 or ' ' ear-flower " ) . Up to the present day the 

 identity of this plant has remained a mystery. 

 The writer has finally succeeded in tracing it to 

 Cymbopetalum penduUflorum, belonging to the 

 Anonaceas. 



Cymbopetalum penduUflorum (Dunal) Baillon 

 was called xocMnacaztli (ear-flower) on account 

 of the resemblance of its three inner petals to 

 the human ear. It occurs in the mountains of 

 truatemala and southern Mexico. 



Sapranthus fceiidus (Rose) Safford the fcetid 

 carrion-flower, is very closely allied to the palanco 

 {Sapranthus nicaraguensis) of Central America. 

 Another species, with flowers having an equally 

 disgusting odor, but with broader petals and an 

 orbicular bract on the peduncle, proves to be 

 identical with the plant described by Dunal as 

 Unona violaceus, and must therefore take the 

 name Sapranthus violaceus (Dunal) Safford. 

 Specimens of it were collected by Dr. J. N. Eose 

 at Rosario, Sinaloa, in 1897 (No. 1842). 



Among the well-known anonas are the sugar- 

 apple, Anona squamosa, usually called anona 

 blanca in Mexico; A, reticulata, the bullock 's- 

 heart, or anona Colorado; A. cherimolia, the 

 Peruvian chirimoya, introduced at a very early 

 date into Mexico; and the pleasantly acidulous- 

 fruited sour-sop, A. muricata, usually known as 

 Guanabana in tropical America. 



Anona purpurea DC, called soncoUo, or sin- 

 cuya, is a species often confused with A. muri- 

 cata, which it resembles in having large flowers 

 with leathery petals and fruit covered with pro- 

 jecting points; but its flowers are sessile and its 

 fruit is not edible, while its leaves differ from 

 those of A. muricata in being much broader and 

 larger. 



Anona longiflora, usually called chirimoya, is 

 very closely allied to A. cherimolia. Its flowers, 

 however, are much larger and its leaves, covered 

 with velvety pubescence beneath, are broader and 

 more obtuse. It was first described by Sereno 

 Watson from specimens collected by Dr. Edward 

 I'almer near Guadalajara in 1886. 



Anona diversifolia n. sp. called izlama, or iUa- 

 matzapotl, has flowers and fruit resembling those 

 of A. squamosa, with the carpels not so closely 

 united as in A. cherimolia, and A. reticulata. It 



is distinguished from aU other Mexican anonas 

 by a large persistent orbicular, clasping bract at 

 the base of the peduncle. The type was collected 

 by Dr. Edward Palmer at Colima, Mexico, m 

 1897 (No. 60). 



W. W. Stockbergee, 

 Corresponding Secretary 



THE PHILOSOPHICAL SOCIETT OP WASHINGTON 



The 689th meeting was held on February 11, 

 1911, President Day in the chair. Two papers 

 were read: 



Thermodynamics of Concentration Cells: Dr. 

 Heney S. Cabhabt, of the University of Mich- 

 igan. 

 The paper was in illustration of the general 



equation expressing the laws of thermodynamics, 



of which the Helmholtz equation for the E.M.J*'. 



of a voltaic cell is an example, viz: 



A = H + T{dA/dT), 



in which B. is the change in the internal energy 

 of the system and A the maximum work or free 

 energy for a reversible process conducted iso- 

 thermally. 



A number of possible cases were outlined and 

 two of them were emphasized for illustration and 

 experimental verification. 



1. When E is constant. Then A=H-\-aT. 

 The relation is then linear and dA/dT is constant. 



2. If with Nernst ("Thermodynamics and 

 Chemistry," Siteungsberichte der Kon. Preuss. 

 Alcad. der Wiss., 1909, 1, 247) it is assumed that 

 H may be expressed in terms of the integral 

 powers of T, then 



H — H„ -\-aT + bT' + cT' + 



By integrating the general equation and substi- 

 tuting this value of H, it is proved that the con- 

 stant a is zero and the two equations for A and 

 H are 



A=A„ + a'T — bT^ — icT' — 



M=U„+ bT- + cT' + 



Nernst assumes that dA/dT =.dR/dT ::=0 in 

 the limit when T = 0. This condition would ex- 

 clude the term a'T and would exclude therefore 

 the case where E is either zero or constant. 



An investigation of the concentration cell 

 Zn amal. dilute/ZnSO^ solution/Zn amal. concen. 

 gave the following data, which are best repre- 

 sented by the linear equation 



£■ = — 0.001455 + 0.00003084 T: 



