MODIFICATION OF VEGETATIVE AND REPRODUCTIVE FUNCTIONS 4 II 
namely, that if plants possess or are capable of synthesizing large carbo- 
hydrate reserves but available nitrogen is limited, then, when such nitrogen 
is supplied, vegetativeness and fruitfulness are both increased. It should 
be noted, however, that though the nitrogen content may be too low for 
fruiting, there is frequently an active and abundant differentiation of parts 
more particularly concerned in sexual reproduction such as buds, flowers, 
spores, and the like, in these carbohydrate-high plan^^-^ and that often such 
plants are not only more easily multiplied by vegetati\ means but actually 
tend more freely to produce specially modified, vegetatively reproductive 
structures. 
On the basis of theory, it should be possible to conceive of at least one 
more relationship which might exist between the carbohydrate and nitro- 
genous materials, namely an abundant source of the latter but a meager 
supply or even a lack of the former. Such a condition actually does prevail 
at least for the non-saprophytic or non-parasitic higher plants when there 
is not sufficient light for synthesis of carbohydrates, or when these are 
limited or removed through insect attacks, pruning, or other agencies. The 
plants are weakly vegetative and non-reproductive. In the case last 
previously discussed, nitrogen and not carbohydrates constituted the 
limiting factor to growth and reproduction, and both were capable of being 
increased through the application of nitrogenous fertilizers; but in the 
instance now under consideration neither vegetativeness nor sexual repro- 
ductivity is increased by additions of nitrogen; it is only when conditions 
are provided such that carbohydrates may be formed in greater amount, 
or are directly supplied, or at least are not artificially removed, that the 
plants become first vigorously vegetative, and with opportunity for further 
increase and accumulation of the carbohydrates in relation to the nitro- 
genous nutrients they become sexually reproductive. Because of the failure 
clearly to differentiate between these two types of the weakly-vegetative 
non-reproductive condition, much of the conflict of ideas regarding the 
means by which vegetativeness or reproductiveness may be regulated 
seems to have arisen, but on the present conception it is an easy task to 
harmonize the results from many experiments which seemingly are at 
variance, or to explain why apparently the same practice may yield widely 
varying results 
Categorically summarizing the foregoing considerations, on hypothetical 
grounds supported by a limited number of definite chemical analyses made 
on tomato and on some other species of plants, and on the basis of various 
suggestions by many workers, we have the following: 
Class I. Though there be present an abundance of nitrogenous nutri- 
ents, with a low carbohydrate supply, vegetative extension occurs but slowly 
and sexual reproduction scarcely at all. There is complete or nearly 
complete absence of blossoms, vegetation is weak, the stems are very 
slender in comparison to their length and are soft and succulent with little 
