DEVELOPMENT. 73 



is not particularly distressed at a wet growing season, but 

 he looks forward with hope to a relatively dry, hot period 

 for the corn to ripen. Of great practical importance also 

 is it to note the different effects of manures as particularly 

 observed at Kothamsted ; some, such as nitrogenous ma- 

 nures, stimulating growth more especially ; others, such 

 as the alkalis and superphosphates, being more particu- 

 larly favorable to the ripening of the seed or the consoli- 

 dation of the straw by the formation of woody fibre. 



Growth is the same throughout all plants, but the 

 mode of development is much more specialized. In its 

 initial stages, the atom of protoplasm that is to be the 

 future potato plant, is not appreciably different from 

 that which is destined to grow into a wheat plant or into 

 a fruit tree. While growth is common to all plants and 

 uniform in character, development is special and different, 

 less or more, in the case of each particular species or kind 

 of plant. Outward conditions greatly influence the 

 amount of growth, while they have relatively less influ- 

 ence on the extent, still less on the direction of develop- 

 ment in the individual plant. 



Inheritance. A particular kind of plant, therefore, 

 may retain its characteristics year after year, century 

 after century, age after age, if the conditions are not 

 greatly altered, because the successor follows, in the 

 course of its development, the same lines as its predeces- 

 sor did. It is thus by hereditary transmission that the 

 characters of plants are perpetuated. 



Variation Selection, But the course of development 

 in the offspring is not always and in all cases the same as 

 in the parents. On the contrary, there is a certain range 

 of variation, by virtue of which a seedling plant does not 

 exactly reproduce either of the parental forms ; indeed, 

 as it is of mixed origin, it could not be expected to do so. 

 4 



