6 CIRCULAR NO. 116, BUREAU OF PLANT INDUSTRY. 



which we have called citranges and which are adapted to culture 

 throughout most of the cotton belt. They will provide a home- 

 grown substitute for lemons for 10,000,000 people of the South. 

 ' Life-history study has brought out the fact that the hardiness of 

 the hybrids (citranges) of Citrus trifoliata, like that of most other 

 plants, is dependent on their condition when exposed to cold. An 

 interval of hot weather in early spring forces these hybrids into a 

 tender growth and they are then liable to frost injury. In the mean- 

 time investigations have shown that the kumquat possesses to a high 

 degree another kind of hardiness due to extreme dormancy in winter; 

 in other words, the kumquat can support weeks of hot weather with- 

 out starting into new growth. Here, then, we have two kinds of 

 hardiness existing in separate plants— the ability to resist extreme 

 cold in G. trifoliata and the ability to withstand untimely spells of 

 hot weather in the kumquat. When these facts were brought out the 

 breeding problem was greatly simplified. It became obvious at 

 once that the use of the kumquat in hybrids would give us plants able 

 to resist injury from hot weather followed by frosts. The latest crea- 

 tion in the way of hardy citrus fruits made by following up this lead 

 is the limequat, obtained by crossing the common West Indian lime 

 with the kumquat. 



The lime is known to all growers as the tenderest of all the citrus 

 fruits. Lime trees are frequently frozen to the ground when oranges 

 and even lemons escape with little injury. This is due to extremely 

 slight dormancv. even a few days of warm weather in winter being 

 sufficient to start a new growth, which is then nipped by the first 

 succeeding frost. The kumquat is admirably adapted by its physio- 

 logical constitution to remedy this defect, and fortunately its fruit, 

 like the lime, contains an agreeable acid juice, and instead of having 

 a disagreeable oil in the peeling, like Citrus trifoliata, the oil of the 

 kumquat is so mildly flavored that the peeling is edible, having a 

 pleasantly aromatic flavor. 



Thus plant life history investigations pointed the way to a 

 breeding experiment which was carried out in the spring of 1909. 

 Already the hybrids made at that time have fruited abundantly and 

 have fully met our expectations. The limequat proves to be a new 

 race of limes able to grow without protection in extreme northern 

 Florida and probably suitable for culture throughout the warmer 

 parts of the Gulf coast. 



The fruits vary in size from that of a large kumquat to that of a 

 small lime, and their flavor varies from mildly acid to as acid as the 

 sourest lime. Here we have a new race of hardy fruits admirably 

 adapted to our own conditions obtained by combining two fruits hav- 

 ing very unlike life-history requirements; one of them but poorly 



[Cir. 116] 



