14 BULLETIN 3 3, POETO EICO EXPERIMENT STATION 



longevity of trees which are budded on lemon stock is said to be less 

 than that of those budded on the other stocks, but this fact was not 

 established. 



Lemon is said to be more severely attacked by foot rot than is 

 grapefruit, whereas the sour-orange stock is reputed to be practically 

 immune. This fact could not be substantiated in field studies be- 

 cause all the older trees were budded too low to permit of learning 

 whether gumming started in the stock or in the bud. In most of the 

 groves gumming of various kinds is as prevalent on trees budded on 

 sour-orange stock as on those budded on lemon stock, although in 

 one grove those budded on lemon stock were found to be the most 

 affected. 



The sour orange may be used as stock for sweet orange, but is 

 less desirable for grapefruit than is grapefruit stock. The sour 

 orange may be planted in any good grade of loose loam, but should 

 never be planted in extremely light or in extremely heavy soils. 



The sweet orange as a stock has not received a thorough trial in 

 Porto Rico, and may be worthy of consideration. The growth of the 

 seedling tree in all types of soil indicates that it may prove to be a 

 desirable stock, at least for the orange. 



The grapefruit may be used as stock for grapefruit, and un- 

 doubtedly for orange as well, although it has not been used for the 

 latter in Porto Eico. It may be planted on any fair grade of soil, 

 but does not thrive as well as the rough lemon in very light sand or 

 in very heavy clay. 



PROPAGATION 



SELECTION OF SEED 



In commercial citrus growing the foundation of the tree is the seed. 

 The seedling is planted either for the purpose of producing fruit 

 as such, or for use as stock. Seedling trees may produce desirable 

 fruit in abundance, as is well illustrated by the thousands of seed- 

 ling orange trees grown in Porto Rico. The fruit is variable, how- 

 ever, and therefore not so valuable as that from budded trees. The 

 difference in value may be too small to warrant the planting of 

 budded trees in coffee plantations, especially where cultivation other 

 than weeding is impracticable. In cultivated groves, on the other 

 hand, where intensive culture is practiced, the cost is too great to 

 risk the planting of seedlings. The seed should be carefully selected 

 regardless of whether the seedlings are wanted for fruit or for use as 

 stock. Seed selection always pays notwithstanding the fact that the 

 seedlings do not always reproduce the desirable characters of the 

 parent tree. 



If the seedling is to serve as stock, the selection may be con- 

 fined to tree characters only, in which case the primary require- 

 ments of the mother tree are vigor and size. Health may well 

 be considered also and perhaps shape, but prolificacy and fruit 

 characters are immaterial factors. If, on the other hand, the seed- 

 ling tree is to bear fruit, the mother tree must be selected for fruit 

 as well as for tree characters. The tree must be large, vigorous, 

 well shaped, healthy, prolific, and produce fruit of such color, shape, 

 and quality as the market demands. 



