XXXV. UMBELLIFER2E. 175 



nerves or ribs, occasionally expanded into urings, and underneath 

 or within the pericarp are often longitudinal channels, called 

 vittas, filled with an oily or resinous substance. Embryo minute, 

 in a horny albumen, which either fills the seed or is deeply 

 furrowed or excavated on the inner face. 



A numerous family, more or less represented nearly all over the 

 globe; but the species are comparatively few in high northern lati- 

 tudes, as well as within the topics, their great centre being western 

 Asia and the Mediterranean region. Their inflorescence, and the struc- 

 ture of their flowers, distinguish them at once from all other families, 

 except that of the Aralias, and these have either more than 2 styles, 

 or the fruit is a berry. But the subdivision of Umbellifers into genera 

 is much more difficult. Linnaeus marked out several which were 

 natural, but without definite characters to distinguish them ; and the 

 modern genera, founded upon a nice appreciation of minute differences 

 in the fruit and seed, are often very artificial, or still more frequently 

 reduced to single species, and as artificial as those of CrucifercB and 

 Composite. These minute characters are moreover in many cases very 

 difficult to ascertain. I have, therefore, in the following Analytical 

 Key, endeavoured to lead to the determination of the species, as far 

 as possible, by more salient though less absolute characters, which may 

 suffice in a great measure for the few British species, although, even for 

 them, the minute variations of the fruit cannot be wholly dispensed 

 with. For this purpose it is essential to have the fruit quite ripe. It 

 must then be cut across, and if a horizontal slice is placed under a lens, 

 the general form, the ribs and furrows of the pericarp, and the vittas, 

 will clearly appear. When the fruit is described as laterally compressed, 

 this slice is of an oval form, the division between the carpels being 

 across the narrow diameter ; where it* is flattened from front to back, 

 (dorsally) the division is across the broadest diameter. In Seseli and 

 other genera, where the fruit is not compressed, the horizontal slice is 

 orbicular. Where the albumen is furrowed, its transverse section 

 assumes a more or less half-moon or kidney shape. 



-/ Leaves undivided 2 



\ Leaves palmate or pinnate, or variously dissected 3 



? Leaves quite entire, grass-like or ovate. Flowers yellow . . 13. BUPLBVRUM. 



2 { Leaves rounded, crenate or peltate. Aquatic or marsh plant, with small 



( heads or whorls of flowers 1. HYDROCOTYLE. 



( Leaves and globular heads of flowers very prickly ... 4. EKYNGIUM. 



3 \ Leaves and stems very thick and succulent 21. CRITHMUM. 



( Leaves neither prickly nor fleshy 4 



( Fruit covered with prickles or bristles or hairs, or with toothed or sinuate 



i\ ribs 5 



( Fruit glabrous and smooth, or with entire ribs or wings 12 



5 / Leaves orbicular or palmate. Umbels simple or irregularly compound . . 6 



\ Leaves pinnate or much dissected. Umbels usually compound . . .7 



( Flowers in small heads, without involucre. Fruit prickly . 2. SANICULA. 



6-< Flowers in simple or irregularly compound umbels. Involucre of many 



( bracts. Fruit rough, with sinuate or toothed ribs ... 3. ASTRANTIA. 



Fruit covered with bristles or prickles or hairs . 8 



Fruit glabrous, with sinuate riba 33. CONIUM. 



Fruit flat, with a thick border 26. TORDYLIUM. 



Fruit ovoid, not bordered -9 



Bracts of the involucre mostly piunatifld 32. DAUCUS. 



Bracts of the involucre entire or noue 10 



