The Sources of Nectar and Pollen 363 
of southern California secrete nectar in abundance only 
if there is sufficient rainfall while the plants are growing, 
preparatory to flowering. Because of this fact, the bee¬ 
keepers of that region carefully watch the records of rain¬ 
fall during the winter to judge as to their prospects for a 
heavy honey-flow in the summer. The physiology of nec¬ 
tar-secretion is so little understood, by beekeepers at any 
rate, that we do not know the relative importance of tem¬ 
perature, humidity, barometric pressure and other environ¬ 
mental factors in bringing about abundant secretion. If 
these influences were more carefully studied, the beekeeper 
could better forecast his crop and plan his work day by day 
during the season. As it is, he relies on his unbounded 
„ hope of success to carry him through. 
Advantages of swamp sources. 
Since plants which grow in swamps are less subject to 
changes in available moisture and usually get an abundance, 
the swamp honey-plants are usually more dependable than 
those growing in dry soils. In swamp lands, too, the honey- 
plants are less liable to destruction through agricultural 
operations and conditions are more likely to remain the same 
year after year. These facts should be more generally 
recognized by beekeepers seeking new locations for the es¬ 
tablishment of apiaries. The tree sources are usually more 
dependable than smaller plants. 
Cultivation of plants for nectar. 
It was stated earlier in this chapter that the beekeeper 
does not cultivate anything especially for his bees. This 
has been tried several times without profit. However, 
plants which are nectar-producers and which also have a 
value in some other respect may often be cultivated with 
profit to the beekeeper. Alsike clover is an excellent honey- 
plant. and many beekeepers have materially improved their 
ranges, either by planting this clover as a forage plant or 
by encouraging neighboring farmers to do so. Buckwheat, 
