338 NINETEENTH REPORT. 



so taken^ are not soil temperatures, and have not the effect on growth 

 that the latter may have_, is appreciated; they are given that a general 

 conception of heat and cold conditions, under which the work took place, 

 may be more fully understood. Other weather reports are taken 

 directly from the records of the U. S. Weather Bureau of East Lansing. 

 (Appendix, Tables I, II, III, IV.) It will be noted that the season was 

 an ideal one for such an experiment, due to the long continued dry 

 weather of July and August, and this must be borne in mind wlien com- 

 paring the growth of root systems of parts II, III and IV of each section 

 of the experiment. 



Before starting the experiment, all of the seed beds used had pre- 

 viously been attacked by a damping off fungus, and in the case of Pinus 

 resinosa the number of seedlings so depleted that full data could not 

 be secured on beds I, 1 1 and III at the end of the experiment. For this 

 reason the photograph of bunches of 50 seedlings from each bed of P. 

 resinosa were not available, tliougli a photograph of two seedlings from 

 each section was made. 



The photographs included in this report were made by Mr. W. I. 

 Gilson of the forestry Department. The groups of seedlings photo- 

 graphed number 50 in every case, unless otherwise designated, and the 

 conditions under which they were grown is shown in the photograph. 

 The graphs were plotted from the data collected and given here in 

 tabulated form. 



PINUS STROBUS. 



The seeds of Pinus strobus were planted in the fall of 1915 (Nov. 19). 

 The first measurements, taken after the beginning of the experiment, 

 (June 28, 1916) were made at that time, and show practically tlie same 

 figures for all four parts of the experiment. On account of the scarcity 

 of the plants, due to their having damped off earlier in the season, only 

 a few were dug and measurements made of two rei3resentative plants. 

 These figures are given below : 



Hypocotyl. Tap Root. 



3.0 cm. 3.5 cm. 



3.0 3.5 



6.0 7.0 



Av. 8.0 Av. 3.5 



On July 5, 1916, measurements were made of two representative plants 

 from each of the four parts of the experiment and are given below under 

 the headings I, II, III and IV, whicli have been explained previously. 



