PINE-APPLE BIENNIAL COURSE. 355 



have denominated the biennial course was first brought into 

 notice by Abercrombie, and more recently has been strenu- 

 ously recommended by Baldwin. Its chief feature is the 

 acceleration of the growth of the plants by the application 

 of higher temperatures than it was formerly supposed they 

 would flourish in. They are, in fact, made to attain the 

 growth of two summers in the course of one year. 



About the beginning of March, the most forward of the 

 plants potted over winter, or the suckers kept in tan, are 

 taken out, the earth or tan taken away, and the roots 

 shortened. They are then put into pots about five inches 

 in diameter, which are plunged into frames or pits heated 

 with tan or stable-litter. They are shaded as usual, and, 

 after they begin to grow, receive moderate waterings. 

 When the roots appear around the balls of soil, which will 

 be about the middle of June, the plants are again shifted 

 into larger pots from six to seven inches in diameter, and, 

 if the heat be declining, are removed into other pits or 

 beds. In the beginning of August they are transferred 

 into large pots, in which, unless they are intended for early 

 spring forcing, they stand during the winter ; and in Feb- 

 ruary they are finally shifted into pots twelve or fourteen 

 inches in diameter. For spring forcing, the last shifting 

 takes place in October, and the pots may be two inches 

 narrower. At every shifting the ball of earth is preserved 

 entire. From March the temperature is gradually in- 

 creased ; little air is admitted, even in strong sunshine, and 

 a lively bottom-heat is kept up by means of repeated lin- 

 ings. When there is danger of scorching the roots, the 

 pots are partially drawn up, or even set upon the surface 

 of the tan. The following table will give an idea of the 

 temperature (Fahrenheit's thermometer) and its progressive 

 increase : 



