Theory of Plant Breeding 
Weissmann’s followers do explain such cases by 
assuming that these practisings and trainings affect the 
germ-cells and so may alter the organism. But amongst 
botanists there has been, from the first, much scepticism 
about germ-plasmas. Such cases as the following are 
very difficult to explain if there is any truth in Weiss- 
mann’s theory.* 
When leaves of begonia are cut off and placed in 
soil, they take root and may form new plants which 
flower and fruit. 
There are no germ-cells in those leaves, only ordinary 
protoplasm, so that, as Professor Henslow pointed out 
(early in the controversy), there is no use in botany for 
a theory of germ-plasmas as distinguished from ordinary 
protoplasm, which indeed is quite mysterious and com- 
plex enough for all theoretical purposes. 
The theory of mutation, which owes its origin to De 
Vries, is still the subject of an active and vigorous con- 
troversy in the botany of to-day. 
It is based on the peculiarities of certain seedlings 
of Oenothera Lamarckiana which De Vries discovered 
growing wild at Hilversum in Holland.” 
_ Now this species was described by Lamarck from 
certain specimens growing in the Paris Botanical Garden, 
and which were supposed to have come from America. 
The wild plant, if it does still grow in America, has not 
been found of late years. On the other hand, it has 
been alleged that it is not a species at all but merely a 
hybrid. If this is true, it is difficult to put any faith in 
those mutants. Even if it were a wild American species, 
it has experienced two distinct changes in climate (to 
Paris and thence to Holland), so that its variations could 
* The excellent account of Weissmannism in Thomson’s ‘‘Heredity” 
should be consulted for further details, and indeed for the whole theory of 
modern evolution. 
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