KEY TO THE GENERA OF MANHATTAN PLANTS. 



45. Wing all around TJlmus 35 



46. Involucre top-shaped, hooks in a circle around the 



upper part Agrimonia 95 



46. Involucre ovoid, hooks all over Xanthium 268 



47. Akene bearing a slender hook, heads globular Ceum 94 



47. Akene with a long villous or plumose tail (style) Clematis 64 



47. Akenes more or less beaked, but not tailed 48 



48 Sepals 3, stem endogenous Alismaceab 4 



48. Sepals 5 or more, or deciduous 49 



49. Sepals 5, with 5 alternating bractlets Potentilla 93 



49. No bractlets '. 50 



50. Sepals deciduous, akenes scarcely flattened, glabrous, 



strongly ribbed Thalictrum 67 



50. Sepals persistent, not ribbed 51 



51. Receptacle much elongated, akenes glabrous Myosurus^Q5 



51 . Receptacle convex or oblong 52 



52. Akenes glabrous, beak oblique Ranunculus 66 



52 Akenes pubescent or woolly, beak straight Anemone 63 



53. Pericarp covered with slender, easily detached, down- 



wardly barbed bristles Sicyos 242 



53. Fruit drupaceous, flesh, very scant Rhus 133 



53. A globose nut with woody ,felty-pu Descent pericarp, 



peduncle of cluster attached to a leaf-like bract, 



trees Tilia 145 



53. In terminal clusters, globular, bearing the superior, 



5-lobed, persistent calyx lobes, herbs Comandra 45 



53 Pericarp thin, fruit enclosed in 5-lobed indurated 



calyx, deflexed on axis Phn/ma 201 



53. Sessile in spikes, 4 to 8 angled or ribbed . 54 



53 Not as above, an akene 55 



54. Nutlets 4-angled Gaura 171 



54. Nutlets 8-ribbed or winged Stenosiphon 172 



55. Endogenous grass or rush-like herbs 56 



55. Exogenous plants 57 



56. Fruit in the axis of a scale, no scale above fruit . . .Cyperaceae 6 



56. Fruit with a scale above and below, leaves 2-ranked 



Gramineae 5 



57. Akene enclosed in an inflated sac, in oblong catkins 58 



57. Akene not thus enclosed 59 



58. Trees, akene oblong, smooth, nerved Ostrya 33 



58. Herbaceous vine, akene orbicular, besprinkled with 



reddish atoms Humulus 38 



59. Sepal 1, folded around the 2-edged akene Cannabis 39 



59. Sepals 3 or 4, or calyx tubular or 4-lobed above Urticaceae 21 



59. Sepals 5 or 6, akene lenticular or 3-angled Polygonaceae 23 



(Compare Ambrosia 269.) 



