A few years ago it was supposed that the running out of varieties of celery was due to a similar cause, that is, to unfavorable environment.  To this was ascribed the pithy quality that characterized some of the varieties.  Upon further investigations, however, it was found that this pithy condition came about through carelessness in seed selection.  There is a more or less inherent tendency in all celery to become pithy, and unless these plants are carefully excluded, the varieties will run out from that cause.

The different varieties of tomatoes, egg plant and the cucurbits do not seem to be especially affected by soil and climate, and in such instances the varieties can be kept up only by rigid selection, no matter how favorable that environment is under which they are grown.  With these plants there is always the inherent tendency to go back more or less to the wild state, and lapse of care in seed selection for a period of only a few years will result in a variety very different from the one which we had in the beginning.

It will be seen from this that in some instances the best plan is for each farmer or gardener to develop his own strains of crops that he grows, while in other cases it is best to leave the selection to those that are working in a more favored environment so far as those varieties are concerned.

There still remains to be considered the plants that are propagated asexually, like potatoes and all our cultivated fruits.  From the fact that a number of our standard varieties of apples and some other fruits date back one hundred years or more, and are still as productive as at the beginning, it is evident that some asexually propagated varieties may be considered almost fixed or permanent.

[Illustration:  Niobe willow (Salix vitellina, var. pendula nova), on campus N.D.  Agri.  College, Fargo.]

The buds or scions from which new trees are started are taken indiscriminately from the bearing trees, and since there is no great variation in them the varieties do not tend to change.  Whether they could be improved by taking scions from only the most productive trees is still a question.  There are some who consider this possible, but we do not yet have enough experimental evidence to establish it as a fact.  So far it would seem that about the only crop which is propagated asexually that is likely to deteriorate, or is capable of improvement, is one that is directly modified by soil and climate.

The potato is the most striking example of this class of crops.  It is well known that the potato responds very readily in the matter of size, yield and quality to certain types of soil and climatic conditions.  It is also known that the qualities thus acquired seem to be more or less permanent; that is, that potatoes brought from the north, especially those which have been grown in heavy soil, will produce a crop some ten days earlier and thirty per cent larger than a