XXXU INTRODUCTION TO BOTANY. 



frcqiiontly to enable plants usually annual to live through the 

 M-intor. Flowers in a maritime variety are often much fewer, 

 but not smaller. 



The luxuriance of i)lants s^-owinG: isolated in a rich soil, and the 

 dwarf, stunted character of those crowded in poor soil are well 

 known. It is also well known how gradually the specimens of 

 a species become stunted as we advance into the cold, damp 

 regions of the sumndts of high mountain-ranges, or into high 

 northern latitudes ; and yet it is very frequently for want of 

 attention to these circumstances that numbers of false species 

 have been added to enumerations and Floras. Luxuriance en- 

 tails not only increase of size of the whole plant or of particular 

 parts, but increase of number of branches, or leaves, or leaflets 

 of a compound leaf ; or it may diminish the hairiness of the 

 plant or induce thorns to grow out into branches, etc. 



Capsules which, while growing, lie upon or close to the groimd, will 

 often become larger, more succulent, and less readily dehiscent, 

 than those which are not so exposed to the moisture of the 

 soil. 



Herbs eaten do\\Ti by sheep or cattle, or crushed underfoot, or 

 burnt over, or otherwise checked in their gro^\i:h, or trees or 

 shrubs cut down to the groimd, if then exposed to favourable 

 cii'Ciimstances of soil and climate, will send up luxui'iant side- 

 shoots, often so different in the form of their leaves, in their 

 ramification and inflorescence, as to be scarcely recognizable for 

 the same species. 



Annuals which have germinated in spring and flowered without 

 check, will often be very diflerent in aspect from indi\dduals 

 of the same species, which having germinated later, are stopped 

 by summer droughts or the approach of winter, and only flower 

 the following season upon a second growth. The latter have 

 often been mistaken for perennials. 



Hybrids, or crosses between two species, come under the category 

 of anomalies from a known cause. Frequent as they are in 

 gardens, where they are artificially produced, they are probably 

 rare in nature. Absolute proof of the origin of a plant found 

 wild is of course impossrtjle ; but it is pretty generally agreed 

 that the following particiilars must always coexist in a wild 

 hybrid. It pai'takes of the characters of its two parents ; it is 

 to be foimd isolated or almost isolated, in places where the two 

 parents are abundant ; if there are two or three, they will 

 generally be dissimilar from each other, one partaking mor • of 

 one parent, another of the other ; it seldom ripens good seed ; 

 it will never be foimd where one of the parents grows alone. 

 ^ATiere two supposed species grow together, intermixed with 

 numerous intermediates bearing good seed, and passing more or 

 less gradually from the one to the other, it may generally be 

 concluded that the whole are varieties of one species. The 

 beginner, however, must be very cautious not to set dowTi a 

 specimen as intermediate between two species, because it 

 appears to be so in some, even the most striking characters, 

 such as stature and foliage. Extreme varieties of one species 

 are connected together by transitions in all their characters, 

 but these transitions are not all observable in the same speci- 

 men. The observation of a single intermediate is, therefore, of 

 little value, unless it be one link in a long series of intermediate 

 forms, and, when met with, should lead to the search for other 

 connectina: links. 



