218 BOTANY 
large groups of plants, whose leaves and stems may 
differ enormously, the flowers are practically the same. 
The kowhai flower is the same type as that of the pea, 
but one plant is a-shrubby tree while the other is a 
herb. Compare again the hard leathery leaves of many 
olearias with the soft spoon-shaped ones of the field 
daisy. Yet the flower is practically the same in both. 
The explanation is simple. It is through its vegetative 
organs that a plant comes into relation with its 
environment, and, therefore, in these, to meet changes 
in its surroundings, modifications have arisen. The 
reproductive organs are concerned always with the 
same thing—the production of the seed, and as, 
speaking generally, the same method will serve this 
purpose in almost any environment, these organs have 
undergone but little change. 
It would seem from their close resemblance that 
there are certain plants which at no very remote 
period had a common aneestor. These belong to the 
same species. There are certain groups of species 
which from their general resemblance to each other, 
would appear at a period somewhat more remote, to 
have also been derived from the same ancestor. These 
groups of species form a genus. Genera may again be 
grouped into natural orders, and, from the fact that the 
different genera forming any one order show in their 
broader features a close resemblance to one another, it 
seems clear that these, too, at a period still more 
remote, had a common origin. Natural orders or 
families may again be arranged in tribes. Continuing 
further, the groups become progressively larger till 
finally we have the following classification :— 
1. Cryptogams produce no seeds, e.g., ferns. 
2. Phanerog'ams produce seeds. 
(a) Gymnosperms have naked ovules, 2.¢., not 
enclosed in an ovary, e.g., the pine. 
