962 ONONIS. | CLASS XVII. ORDER III. 
less numerous, forming an imperfect spike. lowers sessile, or on a 
short footstalk, large, handsome, of a bright rose colour, striated with 
darker veins. Calya persistent, of five linear teeth, much shorter 
than the corolla, enveloping and much longer than the legume, 
downy, and often glandulous. Legume obliquely ovate, or rhomboid, 
downy, bearing two or three seeds, rough, with small elevated tuber- 
cular points. 
Habitat.—Barren pastures, heaths, borders of fields, and waste 
places. 
Perennial ; flowering from June to August. 
Xest-harrow is an extremely uncertain plant in size ; it varies from 
three or four inches to almost as many feet, and is either erect or 
becoming erect from a prostrate base, or it is altogether prostrate, 
and putting out roots occasionally from its joints, and is then 
creeping; and according to the dry or moist nature of the soil in 
which it grows it is simple, or its branches are furnished with 
terminal and often lateral spines; hence it has received different 
names, as O. spinosa, O. repens, and O. arvensis, of Linn., and the 
smaller, more rigid and spiny specimens are the O. antiquorum of the 
same author; but by removing a spiny plant growing in a dry soil to 
a moist and more favourable place of growth, it will soon lose its 
spines, and assume either the appearance of O. repens or O. arvensis. 
This adaptation of vegetables to circumstances is a remarkable and 
curious power in many tribes of plants natural to heaths, moors, and 
arid places ; and for a few minutes let us arrest the attention of the 
student to a brief consideration of their physiological condition. In 
open and sterile parts of the country there are but few plants that 
will grow and flourish as well as under more favoured conditions, and 
these will require a protective means to secure their propaga. 
tion under the unfavourable conditions of their growth : for few are 
enabled to produce more than a scanty number of seeds, and these, 
unless protected, would probably be destroyed by cattle. Nature, 
therefore, has provided such plants with defensive arms to guard them 
against such evils, and to protect their progeny from being cut off by 
untimely means. The means by which the abundant increase 
of the species by seed is prevented, (viz., the barrenness of the soil), 
is at the same time the power used by nature to protect the parent, 
and secure the developement of her smaller number of progeny: for 
the scanty supply of nutriment which the soil affords, renders the 
plant more rigid, and its buds, which under other and more favourable 
circumstances would be developed, become abortive, and are formed 
by starvation into spines, as an armour of defence ; and according to 
the supply of food which it obtains, so is regulated the growth, 
developement, and produce of the plant. When much seed is pro- 
duced, there is a great certainty of its propagating the species, and 
the plant then seems less careful to protect it ; but when the seeds are 
