REST HARROW. — COMMON FERN. 



27 



inoii rest harrow, or Cammock, and by botanists the " Ono- 

 nis arvensis." It is found on barren, sandy fields, and on 

 way-sides, and flowers from June to September. The flowers 

 are nearly sessile, and mostly solitary. Stem hairy. Branches 

 at length spinous. Leaves generally simple, entire towards 

 their base. Root perennial, woody, blackish. Stems rather 

 erect, or procumbent, annual, round, woody, leafy, hairy, 

 spinous when old. Leaves alternate, stalked, elliptically 

 wedge-shaped, linear, roughish ; the lower ones often ter- 

 nate. Stipulas very large, ovate, embracing the stem, 

 toothed. Flowers axillary, sohtary, sHghtly stalked, ele- 

 gantly rose-coloured. Seeds dotted with tubercles. 



Some botanists make a distinction between the " Ononis 

 arvensis" and the " Ononis spinosa" as being distinct species; 

 but Mons. Villars does not distinguish them, alleging that 

 the spines appear with the age of the plant, and growing 

 stronger as the plant grows older. This observation removes 

 much useless reasoning on minute differences. 



The rest harrow has a strong creeping root, which spreads 

 far in the ground. There is little danger from the seeds, and 

 the safest way of eradicating the roots, is to pick them off 

 the land by hand, after they have been well shaken by the 

 harrows in dry weather. They may then be burned in a heap, 

 or rotted with earths into a compost for top-dressing. This 

 weed is not of difficult extirpation : a well-executed fallow will 

 banish it for ever ; and the appearance of it in modern agri- 

 culture shows that there is something wrong in the perform- 

 ance. 



21. The common fern, or the " Pteris aquilina" of botanists, 

 is sometimes found as a weed on corn lands. It belongs to 

 the class and order Cryptogamia fihces " of Linneus, and 

 the natural order " Filices" of Jussieu. 



Generic character. — Fructification in an uninterrupted 

 marginal line. Involucre from the margin of the frond turned 

 in, uninterrupted, separating on the inner side. 



The common fern or brake is the original type of the 

 genus, and is the FiKx scemina" of old writers. The frond 

 is in three deep divisions. Branches doubly pinnate. Leaf- 



