STATISTICS OF THE ORDER CRUCIFERA. 403 
cumstances, will live and propagate by division at the crown. 
Crambe maritima is another plant which divides at the crown of 
the root, and is said to be perennial, but it is not endowed with 
so great self-propagating energy as the Horse-radish, possesses. 
Dentaria creeps horizontally, and where it establishes itself will 
retain its hold of the ground, if left unmolested. Lepidium 
Draba and L. latifolium have long, creeping roots, and are capable 
of a very prolonged existence. A few rare species of Crucifere, as 
Draba rupestris, D. aizoides, Thlaspi alpestre, etc., are accounted 
perennial, but their duration is probably not many seasons long. / “: 
As several species of Crucifere may be found in early spring and 
till late in the autumn, and one of them, viz. Capsella Bursa- 
pastoris, always, so in like mavner they are found in all sorts of 
habitats: they flower in all seasons and abound in all situations. 
What has been said in reference to the duration of the majority 
of the species will serve to point out, with rare exceptions, their 
place of growth. Annual plants generally grow in arable ground, 
or where the soil is pulverized at least once a year. Hence the 
Crucifere are chiefly agrarial plants, i.e. grow in cornfields or in 
gardens, or on rubbish or on manure-heaps, or by roadsides or where 
the ground is more or less broken ; but there is no habitat where 
some of them are not found, from the coast-line to the elevated 
alpine rocks, and from the low, boggy marsh or river-bank to the 
dry, upland pasture. Both exposed and sheltered places produce 
these plants: they grow close to our dwellings, on our roofs and 
walls, and at the very bottom of our mountain lakes. Some are 
confined to the seashores,—either to the sand and gravel which 
abound there, or to the rocks which are continually moistened 
with the salt spray. These species are called littoral plants, from 
littus, the shore. Cakile, Crambe, and Raphanus maritimus grow 
on our sandy seacoasts, and Scurvy-grass on the muddy shores 
both of the ocean and tidal rivers. One of the British Stocks 
grows on the seashore ; the other, Matthiola incana, on maritime 
rocks often far beyond the reach of the most adventurous col- 
lector. Brassica oleracea is a maritime cliff-plant, and Sinapis 
_monensis and 8. Cheiranihus grow on the shore. Several plants 
are said to thrive best near the sea, viz. Senebiera didyma; but 
this plant grows abundantly about Kingswood, near Bristol, 
which is several miles distant from the sea. 
Lepidium latifolium is reported to grow near the sea, but it is 
