1890 



Journal of Applied Microscopy 



METHODS IN PLANT PHYSIOLOGY. 



II. 



GROWTH— Continued. 

 4. To Determine the Distribution of Growth in Roots. Almost any seedlings 

 having straight roots from 2 to 8 cm. long are suitable ; they should be marked 

 with India ink for a distance of 1 cm. at intervals of 1 mm., beginning at the 

 tip. The ink may be applied with a fine brush or with a match which has been 

 sharpened to a " feather point." Ganong^ has proposed a very successful 



method of marking roots by the use of 

 a thread stretched by the spring of a 

 piece of wire. If a drop of ink be 

 placed on the thread and allowed to soak 

 in, very even marks may be made with 

 it without any danger of injury to the 

 plant. The thread and wire may be 

 mounted in a needle-holder. When the 

 ink is dry, the root should be immersed 

 in water for a moment and then sus- 

 pended in a damp chamber. 



The damp chamber is so important 

 in all physiological work that it may not 

 be out of place here to give the details 

 of its construction. Select a glass jar 

 suitable to the size and number of seed- 

 lings to be used, line the sides with filter 

 paper, place water in the bottom of the 

 jar to a depth of I or '2 cm. and allow 

 the paper lining to become saturated ; 

 also line the lower side of the cover of the 

 chamber with moist filter paper. For 

 suspending the seedlings use a small wooden or glass bar about 1 cm. shorter 

 than the diameter of the jar, cut two strips of white blotting paper the same 

 width and length as the bar ; moisten the strips with water and lay them on the 

 bar, slipping a rubber band over one end. This end is now clamped in a vise 

 and the strips of paper separated with one hand, while with the other a seed- 

 ling is slipped in between them up next to the rubber band, the strips are then 

 laid together and another rubber band is slipped on next the seedling. Con- 

 tinue inserting seedlings in this way until the bar is full (Fig. 1). Wedge the 

 bar in the jar with a short piece of rubber tubing. Fastened in this way the 

 seedling is uninjured, the root and stem are perfectly free to grow, and no 

 difficulty arises from Sach's curvature. Within a few minutes after preparation 

 the atmosphere of the damp chamber is saturated with moisture in which the 

 seedlings will grow as long as the food supply lasts. 

 1. Ganong, W. F. Bot. Gaz. 27. 



Fu;. 1. — A Damp Chaml)er. The bar is 

 lifted out in order to show the manner of 

 suspending the seedlings. 



