& 
BOTANICAL APHORISMS. 203 
they call blotched. When the margin is yellow, the 
leaves are called folia aurata; when the centre has a 
yellow spot, they are called folia aureo-variegata ; 
when the leaf is white on the margin, it is called 
folium argentco, s. albo-marginatum; when it is white 
‘in the centre, it is called folium albo, s. argenteo- 
variegatum. 
§ 203. 
Besides in colour, leaves change also in number, 
breadth, figure and parts. In number leaves change 
only when they are compound or opposite. ‘They 
vary often in breadth, so that an oval leaf fre- 
quently becomes oblong, &c. Culture often changes 
the figure of leaves, especially in rich soils. Of 
this we have an example in the common colewort ; 
and other plants acquire sometimes waved or crisped 
leaves. 
The different divisions of leaves often change re- 
markably the appearance of a plant. The common 
elder, (Sambucus nigra), has sometimes finely cut 
leaves. The alder, (Betula a/nus), has likewise 
lobed or divided leaves ; and many others are sub- 
ject to like varieties. Culture is the true touch- 
stone of plants; by frequent sowing the seeds we 
can determine with certainty what are varieties, and 
what are species. ‘This is the only means of arriy- 
ing at the truth. | | 
§ 204. 
When the student has become acquainted with 
these rules, and by practice has attained a readi- 
| ness 
