THE TROPAGATION OF PLANTS, WITHOUT SEEDS. 



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THE PROPAGATION OF PLANTS, WITHOUT SEEDS. 

 By Rev. Prof. G. Henslow, M.A., V.M.H., &c. 



Lecture to the Students at tlie Society's Gardens, June 12, 1901. 



The reproductive system "proper " of plants consists, of course, of their 

 flowers and the resulting fruits and seeds. These have a more or less* 

 great facility for distribution, thereby enabling the descendants to" escape 

 to a distance from the original habitat of their parents. 



Seed, however, is largely supplemented, and indeed in many cases 

 entirely superseded, by methods of propagation carried on by the vegeta- 

 tive system of flowering plants. We are all familiar with runners, stolons, 

 bulbs, corms, &c., as different methods, which plants have acquired, by 

 means of which they can reproduce themselves independently of seed. 



Moreover, it has been noticed that when a plant has been long pro- 

 pagated entirely by these structures, it appears often to lose the faculty — 

 whether temporarily or permanently it would be hazardous to conjecture 

 — of producing seed. This is the case with the Horse-radish in our gardens. 

 It is said to have been so with the cultivated Saffron Crocus ; and to a 

 large extent it is so with the wild Lesser Celandine, &c. 



Another noticeable feature is that although the particular form, say^ 

 bulb, corm, &c., may be normally subterranean, the power to produce 

 them resides in the living protoplasm of the whole plant ; so that we 

 sometimes find tubers, bulbs, and corms on the aerial parts of plants. 



The question now arises, what were the surrounding conditions which 

 induced these various forms of propagative structures to occur ? 



In former days, botanists were content to describe them and say that 

 the common blue Iris or Garden Flag was characterised by having a 

 rhizome ; Primroses, by a rootstock ; Crocuses, by a corm, ^c. And 

 that was considered sufficient. But evolution has come to the front, and 

 we do not now rest satisfied with facts alone ; we want to find out the- 

 causes of their existence ; as Bacon said : " The End of our Foundation 

 is the knowledge of causes and secret motions of things." 



The questions, then, are, how the environment acts upon plants, and 

 how they respond to it. We cannot always be sure that we are right, but 

 we can frame hypotheses, to be discarded as soon as more certain know- 

 ledge is obtained. 



Let us take the various organs of a plant in order — roots, stems, and 

 branches, buds and leaves, and we will see how they can depart from 

 their normal functions and become means of propagation respectively. 



Roots and Stems.— 1 will here quote what I have elsewhere written 

 upon the possibility of interchanges between the functions of these 

 organs.* 



That roots and stems are structures differentiated from a common 

 and fundamentally identical type is obvious from such facts as the follow- 

 ing : Every detail in the histological elements of the two structures can, 



♦ Origin of Plant Structures, p. 171). 



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