CH. II] SUGAR CULTURE. 29 



been added, to (B), 5 7o glycerine, while to (C) nothing 

 has been added. It is of importance that specimens 

 similar in size and in general vigour shall be selected, and 

 that the specimens should be small in comparison with 

 the volume of water in the beaker. Leave the vessels in 

 the dark room for 5 or 6 days, when the plants in (A), (B) 

 and (C) are to be compared as to condition, growth, and 

 especially as to the contained starch. The chief difficulty 

 experienced is the growth of moulds in the solution. 

 Something may be done by washing the vessels with ^ p.c. 

 corrosive sublimate and then in boiled distilled water; the 

 culture fluids should be boiled and allowed to cool in 

 vessels closed with cotton-wool plugs. [See Chap, iii.] 



Chlorophyll is not necessary for this form of assimila- 

 tion, colourless parts of plants form starch vigorously. 

 The white flowers of Phlox panicidata are especially 

 useful for this experiment. They are simply floated in 

 the above described solutions of sugar or glycerine, control 

 specimens being placed in water. In a few days they 

 become rich in starch, while the control flowers are 

 starchless. The employment of colourless objects, such 

 as white flowers, is especially convenient, since the use of 

 alcohol as a decoloriser is avoided. The flowers must, 

 however, be boiled before being placed in the iodine fluid. 



(39) Formaldehyde. 



Loew' and Bokomy^ have shown that although form- 

 aldehyde is poisonous even in very dilute solutions, yet 

 that oxymethyl natrium sulfonate (which is easily decom- 



' Botan. Gentralblatt, xliv. p. 315. 

 2 Berichte d. D. Bot. Ges. ix. p. 103. 



