in foreign samples ; for as the weed and the 

 crop-plant are harvested together, and the 

 two seeds are somewhat similar in colour, 

 it has escaped detection by the careless 

 and uneducated farmer, and consequently 

 the seedsman has not been particular in 

 their separation. They are, however, very 

 different in shape. The best way to avoid 

 errors of this kind is to buy the Sainfoin 

 seed decorticated. The leaves of both 

 plants are pinnate, but the leaflets of the 

 Sainfoin are entire, whilst those of the 

 burnet have deep saw-like teeth. [J. B.] 



ONOCLEA. A very distinct genus of 

 ferns associated with the Aspidiece. The 

 principal and perhaps only species is 0. 

 sensibilis, sometimes called the Sensitive 

 Fern, but having no other claim to this 

 name beyond the fact of its speedily wither- 

 ing when cut. This has a creeping rhi- 

 zome, and dimorphous fronds, the sterile 

 ones pinnato-pinnatifid, bright-green, with 

 closely reticulated veins, and the fertile 

 bipinnate, with small incurved bacciform 

 pinnules, in which lie a few large globose 

 sori having a special cucullate indusium 

 behind each. It is North American, and 

 quite hardy in our ferneries. [T. M.] 



ONOM ATOLOGY. That branch of know- 

 ledge which relates to the rules to be ob- 

 served in the construction of names. 



| ONONIS. A numerous genus of Legu- 

 | minosce, abounding principally in the coun- 

 tries bordering on the Mediterranean. 

 None of the species grow very tall, the ma- 

 jority being undershrubs about two feet 

 high. They have trifoliate or rarely sim- 

 ple leaves, with the leaflets generally 

 toothed, and the stipules adhering to the 

 leafstalks ; and solitary yellow or purple 

 flowers growing from the axils of the 

 leaves, but sometimes forming terminal 

 leafy racemes. The calyx is cut into five 

 ! narrow segments ; the upper petal of the 

 | papilionaceous corolla is large and striated, 

 while the two lower ones terminate in a 

 pointed beak, and the stamens are all 

 united into a sheath. The pods are few- 

 seeded and usually inflated. 



0. arvensis is indigenous to this country, 

 where it occurs in barren pastures, on the 

 borders of ill-cultivated fields and similar 

 places. It is usually a low-spreading un- 

 dershrub, often with creeping under- 

 ground stems, but is sometimes more 

 erect and one or two feet high, and has 

 thorns when growing in dry situations. 

 In England its most common name is 

 Restharrow, but in Sussex, Hampshire, 

 and some other counties it is also called 

 Cammock ; and the country people, having 

 the idea that it communicatesits nauseous 

 goat-like odour to the cheese made from 

 the milk of cows who have eaten it, call 

 the cheese so tainted cammocky. The 

 name Restharrow has arisen fromits tough 

 underground roots causing stoppages 

 when harrowing or ploughing fields where 

 it abounds. [A. S.] 



ONOPORDON. A genus of spinous 

 herbaceous plants belonging to the tribe 



Cynaroccphalce, of compound flowers, and 

 distinguished among its congeners by 

 having a pilose pappus, the hairs of which 

 are at the base united into a ring, four- 

 ribbed seeds, and a honeycombed recepta- 

 cle. O. Acanthium, or Cotton-thistle, the 

 only English species, is a common way- 

 side plant, with dull-green woolly very 

 spinous leaves, of which those seated on 

 the stem are prolonged at the base so as to 

 run down the stem, and give it the appear- 

 ance of being armed with prickles on all 

 sides. The stem is three to four feet high 

 or more, branched above, and bears many 

 large heads of dull purple flowers, of which 

 the involucre is nearly globose and very 

 spinous. It is less common in Scotland 

 than in England, but according to Sir W. 

 J. Hooker it is cultivated in the former 

 country as the Scottish thistle. Some 

 foreign species, and among them 0. arabi- 

 cum, are cultivated for the picturesque 

 effect produced by their stately habit of 

 growth, white leaves, and heads of purple 

 flowers. French, Chardon commun ; Ger- 

 man, Zellblume. [0. A. J.] 



ONOSMA. A genus of Boraginacece, con- 

 sisting of scabrous undershrubs, covered 

 with stiff white hairs, and havingnumerous 

 linear or lanceolate leaves, and terminal 

 scorpioid racemes of large yellow or pur- , 

 plish flowers, with a five-parted calyx, a j 

 tubular bell-shaped corolla without scales 

 at the throat, exserted stamens, and ovate 

 stony nuts, affixed to the receptacle by a 

 flat base. The species are found in Middle 

 Asia, and a few in Europe. [J. T. S.] 



ONOSMODIUM. A genus of Boraginacece, 

 differing from Onosma in having a corolla 

 with a ventricose five-parted limb of some- 

 what converging segments. They are 

 North American hispid herbs, with oblong 

 ribbed leaves, and white greenish or yel- 

 lowish flowers, with included anthers. The 

 nuts are ovoid, swollen, and affixed by the 

 flat base to the receptacle. [J. T. S.] 



ONYCHACANTHTJS (including Brava- 

 isia.) A genus of Acanthacece, confined to 

 Mexico and the northern parts of South 

 America, and consisting of two species, 

 O. Cumingii alias Bravaisia fioribunda, 

 and 0. Berlin dcrianus, both large shrubs 

 or small trees of considerable beauty. The 

 leaves are ovate or oblong, glabrous, and 

 petiolated. The panicle is axillary or ter- 

 minal, and bears whitish or yellowish 

 flowers, the calyx of which is five-cleft, and 

 the corolla neai-ly funnel-shaped, and en- 

 closing four stamens. The capsule is ob- 

 loi]Er,smooth, two-celled, and containsfrom 

 four to eight seeds. [B. S.J 



| 0NYCH1HM. A genus of pterideous 

 ferns with decompoundly divided fronds, 

 ; often of a somewhat membranous texture, 

 and with small narrow alternate segments, 

 i They are very elegant plants, and in some 

 1 cases, such as 0. auratum, have the fronds 

 I of a somewhat dimorphous character. The 

 | fertile segments are soriferous along their 

 i margins. The sori are linear or oblong, 

 I with continuous receptacles, and membra- 



