THE FOOD OF PLANTS. 



stand in the open air, e.g., outside the window or behind the open 

 window. The transference of the pollen to the stigma can then 

 be effected by insects. 



As we have said, considerable warming of the food solution, and 

 also deficiency of Oxygen in it, may be very prejudicial to success 

 in cultivating plants by the water-culture method. Wortmaun 3 

 has recently described a simple method for considerably reducing, 

 if not completely eliminating, these dangers, a method which is 

 particularly to be recommended when it is desired to obtain hand- 

 some plants by the method of water culture for purposes of 

 demonstration. We cultivate the plants, viz., in very large vessels. 

 Suitable glasses are to be obtained at a price of 5 marks from 

 Ehrhardt & Metzger in Darmstadt. They are 60 cm. high, 25 

 cm. in diameter, and hold 26J litres of water. We fill the 'glass 

 cylinders, if only demonstration experi- 

 ments are intended, with spring water, 

 introduce the germinated plants (e.g., 

 Phaseolus), and let them vegetate for 

 six days. We then add to the water 

 sufficient nutrient salt (its composition 

 may, e.g., be such as is specified on p. 3) 

 to give a concentration of 1 per cent. 

 After three to four days the strength is 

 raised to 2 per cent., and after three to 

 four days longer to 3 per cent. Every 

 three or four days the food solution is 



thoroughly well stirred up. It need not be renewed, but care 

 must be taken to replace the evaporated water. To shade the 

 roots it is sufficient to wind round the cylinders one to two layers 

 of white linen or woollen. 



For the cover of the culture cylinder we use a round piece 

 of wood, which projects a little beyond the margin of the vessel. 

 The cover is easily prevented from slipping about by driving in a 

 few nails from below. In the middle of it is a hole 3 cm. in 

 diameter, in which the plant can be fixed in the usual way. Just 

 beside this hole is another, in which is fixed a not too thick 

 rod, which serves to support, e.g., a Phaseolus plant. From the 

 central hole a slob about 2'5 cm. broad runs to the periphery 

 of the cover. By means of this the research plant can be readily 

 introduced or taken out. The slot is closed by means of the strip 

 of wood which is removed in making it. The cover, seen from 



FIG. 2. Wooden cover for a 

 culture vessel. 



