180 PROCEEDINGS OF THE AMERICAN ACADEMY 



ties ; (Enoihera tetraptera, Cav. (201) and CE. rosea, Ait. (367) are 

 common Mexican plants. 



Mentzelia aspera, L. (206) is in all collections ; Gronovia scandens, 

 L. (149) is not so common, nor is Turnera Pumilea, L. (134). 



Passiflora fcetida, L. (158''), P. serratifolia, L. (226), and P. diffor- 

 mis, H. B. K. (211); Lagenaria vidgaris, Ser. (318); Sicyos angida- 

 tus, L. (306), an Elaterium ? with only male flowers (258), and male 

 flowers only of another Cucurbitacea (354). 



There are four species of Begonia (261, 268, 334, 370), which will 

 soon be determinable by the forthcoming (15th) volume of De Can- 

 dolle's Prodromus. 



M'yngium fcetidum, L. (260) and Helosciadium leptophyUum, DC. 

 (190, 256, 257) are the commonest subtropical weeds. 



Loranthus Schiedeanus, Cham. & Schlecht. is the only representative 

 of that order. 



The Rubiaceae are a doubtful Spermacoce (181) ; Diodia villosa, DC. 

 (255) ; Richardsonia scabra, St. Hil. (238) which, by the way, inclines 

 to be naturalized in the United States, and is probably Pursh's (Sper- 

 macoce involucrata ; Geophila reniformis, Cham. & Schlecht. (232) ; 

 the common CMoeocca racemosa, isiC(\. (241) ; Psychotria mollis, Poir. ? 

 (246) ; Randia Xalapensis, Mart. & Gal. ? (320) ; flowers of another 

 Randia mismatched with leafy branches of a Casearia (329) ; Boii- 

 vardia ternifolia, Schlecht. (105); Oldenlandia ( Gero7itogea, Cham. 

 Sc Schlecht.) mici-otheca, DC. (200), and fine specimens of the follow- 

 ing apparently new species : — 



Exostema Mexicaniim (sp. nov.) : foliis ovalibus acuminatis basi ro- 

 tundatis vel obtusis breviter petiolatis membranaceis insigniter pinni- 

 nerviis ramisque glabris ; cyma corymbosa composita floribunda flori- 

 busque cinereo-puberulis ; pedicellis ovario clavato longioribus ; calycis 

 limbo brevi quinquefido ; corollaj (albaj ?) lobis tubo sequilongis. — Ar- 

 bor elata, foliis pallidis semipedalibus, corollis polHcaribus, sestivatione 

 generis, i. e. quincuncialiter imbricatis, nee valvatis,* antheris anguste 

 linearibus basifixis. Filamenta epigyna, a coroUse libera (125). 



* Weddell, in his tabular synopsis of the Eucinchonem assigns an aestivation of 

 the valvate type to Exostema ; but it is not so in the genuine Caribtean species, nor 

 in the present one, which is a manifest congener of E. Peruvianum. I know not 

 Bentham's E. occidenlale, in which the aestivation of the corolla is said to be valvate. 

 The wonder is that the manifestly imbricative aestivation in Exostema could have 



