170 



llOSACE^. [Purshia. 



be ranked as species. The serratui'es aud tiifts of hair on the underside of the leaves are undoubtedly variable, 

 and -vve know how little dependence is to be placed upon the foliage of our own Cerasus Padus, a species 

 so nearly allied to this, that M. Seringe (in De Candolle) soeras to doubt if it be really distinct. 



Trie. II. SpiR^EACEiE. DC, 



3. PURSHIA. Be Cand. 



CaL tubulosus 5-fidus, lobis ovatis obtusis. PeL 5 obovata unguiculata cum stanuiiibus 

 25 calycis ore inserta. Ovarium 1 (" 2 ex Br'') oblongum libenim stipitatum pubescenti- 

 glandulosum stylo subulato attenuatum. Stigma lineare laterale longitucline fere styli, 

 pubescens. Ovulum unicum paulo supra basin insertum in parietem loculi adscendens. Ach- 

 enimn (rima longitudinal! dehiscens, DC) oblonguin utrlnque attenuatum, stylo coronatum. 

 Semen obovatum. Integumentum crassum. Albumen? tenue carnosum. Embryo erectus. 

 Cotyledones ovales. Radicula infera. — Frutex ramis erectis, ramuUs brevibus nwnerosis, 

 gemmis squamosis. Folia fasciculata simpUcia S-deniata subtus albida, Flores terminales 

 conferti, Petala filamentaque siccitate ceruginosa, 



1. P. tridentata. (Tab. LVIII.) De Cand. in Linn, Trans, v. 12. p. 158, Prodr. v. 

 2, p. 541. — Tigarea tridentata. Pursh, Fl, Am. v. \, p, 333. t. 15. 



Frutex erectus, cortice cinereo rugoso glabro tectus. Rami stricti subvirgati, ramulis brevibus fescicula- 

 tis onusti. Folia fasciculata semper e gemmis elongatis ramosis squamosis orta, G-8 Uneas longa, cuneata, in 

 petiolum brevem attenuata, apice tiidentata, supra glabriuscula, suhtus albo-tomentosa. Sllpidce minutae tri- 

 angulares. Flores solitarii vel congesti e fasciculis foliorum. Pedunculus brevis, glandulosus. Calyx extus 

 tomentosus, tuba elongato glanduloso glandulis pedicellatis, limho 5-fido, patente, segmentis ovalibus, obtusis. 

 Petala 5, calyce inserta, laciniis alterna, patentia, obovata, obtusa, undulata, venosa, siccitate viiidescentia, 

 basi in unguem attenuata. Stamina 25, ad orem tubi calycis inserta, Filamenta filifonula, siccitate sordide 

 viridia. Antherm subrotundue. Pistillum solitarium, ad basin calycis insertum, et ejus tubo duplo longius, 

 breviter stipitatum. Germen ovali-cyllndraceum, pubescens atque glandulosum uni-ovulatum superne in 

 stylum attenuatum. Stigma lineare, laterale, pubescens. Capsula (seu Acheniuni) 6-7 lineas louga, con- 

 aceo-membranacea, pubescens, ovata, basi apiceqne attenuata, inferne calyce persistente tecta, iudeliiscens, 

 (longitudinaliter dehiscens, DC,^ uiuloculare,monospermum. Loculi paries longitudinaliter striatus. Semen 

 obovatum, nigro-purpureum, prope basin loculi insertum dein erectum. Integumentum crassum, extus minute 

 punctatum : Parenchyma grauulosum intense purpui'eum. Albumen camoso-membranaceura, albidum. Em- 

 bryo obovatus compressus carnosus albus. Cotyledones maguie, crassie. Radicula infera. 



Hab. In the Prairies of the Rocky Mountains, and on the Columbia River. Lewis. " Almost the only 

 shrub to be seen through an Immense tract of barren sandy soil from the head sources of the IVIissouri to the 

 Falls on the Columbia, and from 38° to 48° of north latitude." Douglas. — It does not appeai- that any 

 Botanist has ever gathered this highly interesting plant, except the travellers above-mentioned. From Lewis' 

 Bpecimens of the Tigarea tridentata of Pursh, preserved in Mr. Lambert's Herbarium, Professor De Candolle 

 established the genus Purshia in the Linnaean Transactions. The %ure given by Mr. Pursh is sufficiently 

 faithful for the general appearance of a branch ; but the details of the fructification were still a desideratum. 

 This I have endeavoured to supply by the aid of the beautiful specimens collected by Mr. Douglas. The 

 covering of the seed presents an appearance which I do not quite understand. It is double. The epidei-mis, 

 which is thin and membranous, owes its colour to a deep purple granulated pulp lying between it and the 

 inner lining, which latter is opaque and fleshy, whence I have been led to consider it as albiunen. The t^o 

 coats are easily separated from the intermediate pulpy and granulated substance. 



Tab. LVIIL Purshia tridentata. Fig. 1, Flower from a gemma, natural size, with three leaves; Jig. 2, 

 Flower not quite expanded, magnified; fig. 3, Expanded flower, with the gemma and leaves; fig. 4, 



