106 
IRREGULAR METAMORPHOSIS OF PLANTS. 
Irregular Metamorphosis of Plants. —It is probable that 
all plants have a particular range, in some cases more extended than in 
others, to which they are best suited in consequence of their consti¬ 
tutional peculiarities, which become visible from the effect produced 
by a change of situation, although not appreciable otherwise. The 
two great agents by which they are affected, that is to say, soil and 
atmosphere, will, in their natural situations, be nearly uniform. And 
as long as this uniformity of the conditions under which they exist 
continues, their structure will remain unchanged: but let an alteration 
take place 3 their atmosphere, for instance, change from that of the 
valley to that of the mountain; the soil from alluvial deposit to chalk 
or slate, and the mean temperature under which they are formed fall 
several degrees; or, remove a plant from its native spot and cultivate 
it in the rich soil of a garden for several generations, thus submitting it 
to the effect of what may be called domestication. Under such circum¬ 
stances, an alteration will be produced in the structure of the plant, 
which will become manifest by external characters. This is what is 
called irregular metamorphosis, and may be considered the cause of the 
endless varieties of form into which garden plants are continually sport¬ 
ing. In a wild state, the varieties are comparatively rare ; while, on the 
contrary, new forms, miscalled species, are always starting up in every 
botanic garden. In the garden of Berlin, Link states, that Ziziphora 
dasycintlia , after many years, changed to another form, which might 
be called Z. intermedia . 
But although there is no reasonable doubt that irregular metamor- 
phosis does take place in consequence of some change in the conditions 
under which plants are formed, the cosmica momenta of some writers, 
yet it is certain that we are entirely ignorant of the specific causes by 
which metamorphoses are effected. We know that the cellular tissue, 
and the secreted matter or proper juices, are what chiefly manifest 
their sensibility of change; but beyond this, we know absolutely 
nothing whatever. In this want of information, the simplest manner 
of treating this subject is to take the parts of vegetation in succession, 
and to state what is known of the irregular metamorphosis of each. 
The roots and tubers undergo a vast variety of changes; some of 
which are the effects of domestication, and others produced in wild 
individuals. Some grasses, when growing in situations more dry than 
those to which they have been accustomed, acquire bulbs, as if laying 
by reservoirs of nourishment to meet the casual want of a sufficient 
supply of food. Other roots sport, when domesticated, into various 
forms and colours, as is familiarly exemplified in all those which supply 
our tables. In the turnip the form varies from spherical to depressed. 
