1NTEODUCTION. 



WITHIN the last few years horticulturists generally have evinced 

 an increasing desire to study the physiology and structural 

 affinities of plants, as well as the art of growing them success- 

 fully. This has arisen doubtless from the fact that such know- 

 ledge tends to a clearer understanding of the laws governing 

 the hybridisation of plants, and the great variety of forms 

 they assume when subjected to artificial conditions. Not that 

 botanical science is so far advanced as to be able to explain 

 satisfactorily all the numerous phenomena of plant-life brought 

 to light by cultivators. But much may be expected to result 

 from the combination of science with practice. Experiments 

 will be carried out in a more systematic manner, and the 

 results more carefully recorded by those possessing sufficient 

 knowledge to render their labours interesting beyond the com- 

 mercial value or beauty of the varieties raised. Botanists can 

 only theorise on many questions that gardeners have in their 

 power to prove or disprove. 



Basis of Classification. The characters upon which sys- 

 tematic classification is founded, reside chiefly in the various 

 modifications of the organs of reproduction and the floral en- 

 velopes. Distinguishing the organs of a plant into two sets 

 those concerned in its reproduction, and those that perform its 

 nutrition we expect in a genus some material recognisable 

 difference in the former, or, in other words, we put together in 

 one and the same genus all the species known which have the 

 different parts of their flowers constructed and arranged upon 

 the same plan ; and when there are constant differences between 

 plants which have the same plan of structure we say that these 

 latter are distinct species. Apply this to such a clearly marked 



