190 The Principles of Fruit-growing. 
leguminous, comprising those plants which take only 
such nitrogen as has already been worked over into 
available form by plants or animals; the other class is 
the leguminous plants, comprising those which have 
the power of appropriating and utilizing free nitrogen. 
For purposes of cover and protection, the non-legu- 
minous crops may be just as good as the nitrogen- 
gatherers, and when the fruit plants are growing 
very vigorously they may be decidedly better than the 
others because, by not adding nitrogen, they do not 
over-stimulate the growth. <A rotation of cover crops 
will nearly always be found to be important. It is 
perfectly possible to put so much nitrogen into the 
land that the trees or plants grow too vigorously 
or too late in the season. This may be especially 
apparent upon pcaches, apricots, grapes, and the 
like. It should also be said that some of the most 
useful of these cover crops will not thrive upon hard 
and intractable land, and in such eases a rougher 
and coarser crop must be used. 
The golden scale of cover crops for orehards be- 
gins with rye and ends with crimson clover. Lands 
which are very sandy and leachy, as well as those 
which are hard and lumpy, are usually not adapted to 
the growth of crimson clover, especially in the north. 
Such lands must be gradually ameliorated by the use 
of other plants, and, as a rule, the best plant to 
begin with is rye. This plant thrives upon a great 
variety of soils, it demands little preparation of the 
land, the seeds are large and germinate at a low tem- 
perature, it can be sown late in the season after 
