38 FIELD COLUMBIAN MUSEUM BOTANY, VOL. 2. 



[ALTERNANTHERA SPINOSA Roem. & Schult. 



Specimen 268 of Combs, Santa Clara district of Cienfuegos. 



Although no details of pubescence characters are given in the 

 descriptions of this species, it is safe to conclude that the verticillate 

 branching of the hairs clothing the stem and under surfaces of the 

 leaves has been overlooked. The heads are more strikingly spinifer- 

 ous than the other West Indian species of Alternauthera.] 



ALTERNANTHERA PARONYCHIOIDES St. Hil. Voy. Bre's ii, 2: 43. 



Dry roadsides near Guanica, Porto Rico (725, 748). 



Not readily differentiated by its dense prostrate habit alone from 

 A. repens, but widely removed in its flower characters. Stamens 

 much longer than the short, wide, more or less dentate staminodia. 



LITHOPHILA Sw. Prod. Viq. Ind. Occ. 14 (1788). 



Lithophila muscoides Sw. Philoxerus R. Br. Prod. 416 (1810). 



The genus Lithophila seems so clearly denned in habit and floral 

 structure as to deserve recognition apart both from Iresine and Alter- 

 nanthera. Iresine it is true may sometimes have a capitate inflores- 

 cence, but its flowers are never compressed as in Philoxerus; in cases 

 of capitate inflorescence in Iresine the heads are never enveloped or 

 subtended by leafy bracts as in Philoxerus and Lithophila; while the 

 staminal cup of Iresine has always either the rudiment of a stamino- 

 dium or a rounded or pointed elevation of the margin of the cup where 

 the staminodium would otherwise arise. In Philoxerus as well as in 

 Lithophila, which differs from Philoxerus essentially in having 2 to 3 

 stamens, the sinuses of the cup between filaments and filament- 

 rudiments are so shaped as to preclude the theory of staminodia at 

 any period of the history of their development. Bentham & Hooker's 

 Genera Plantarum describes the cup of Lithophila as simple or den- 

 tate between the filaments. Such dentations will probably be found 

 to be rudiments of the deficient 4th and 5th stamens corresponding 

 to the full number 5. For the proper interpretation of staminodia, it 

 must be remembered that the rudimentary filaments arising on the 

 cupule in the position of the deficient stamens in Lithophila are 

 essentially different in their significance from the teeth or staminodia 

 of Iresine and Alternanthera, which are alternate with the filaments 

 and with the calyx segments, never opposite as in Lithophila. Dr. 

 Kuntze in a discussion of the relationships of the group in his Revisio 

 Plantarum ascribes staminodia also to Philoxerus; in a large number 

 of specimens of Lithophila vermiculata (L) Uline examined, I have not 

 found the slightest indications of them. Grisebach, Flora West Indies, 

 also recognizes this entire absence of alternating staminodia both in 

 Philoxerus and Lithophila as an essential generic character, but he 

 goes a little further and keeps the two apart on the basis of the dif- 

 fering number of stamens. This variability in number of stamens 

 occurs elsewhere in the Amaranthaceae, and certainly can not be justifi- 

 able as a genuine character. From a phylogenetic point of view the 

 creeping or prostrate species of the group seem to be plainly 

 depauperate forms adapting themselves to conditions offering meager 

 nourishment, e. g., sea-shore, sandy or rocky places, etc. The result 



