THE IMPORTANCE OF PHENOLOGICAL 

 OBSERVATIONS. 



Geo. N. Lamb '09. 



That there is an intimate relation between plants and cli- 

 mate or season is a well established truth. Climatic or seasonal 

 factors are not only responsible for the limits in the distribution 

 of plants in the great majority of instances but are directly cor- 

 related with their growth and development. The variable factors 

 upon which the growth of plants depend can be classified as 

 atmospheric, individual, local, and geographical. The atmos- 

 pheric factors are temperature, sunshine, cloudiness, humidity, 

 winds, density of the air, and electricity. Some of the individual 

 factors are the variety of the plant, age, health, and habit. The 

 important local factors are soil moisture and site or situation. 

 The geographical factors are altitude, latitude, and longitude, or, 

 expressed in more general terms, the position on the earth's sur- 

 face. All of these factors have an influence upon plants to a 

 greater or less degree. Such factors as temperature, light, soil, 

 and moisture are most important, but such factors as winds, var- 

 iety and altitude also have their definite influence. Plants in their 

 vegetative processes make a very sensitive response to variations 

 in these factors. The most important response to seasonal vari- 

 ations is in the time of the occurrence of life functions. If there 

 is a lack of moisture or low temperatures in the spring when vege- 

 tation is most rapid this variation is noted very delicately in the 

 delay in appearance of the leaves, flowers, or fruit of the plants. 

 If there is excessive temperature, moisture, or sunshine the re- 

 sult is an earlier appearance of the life functions. Not only are 

 the seasonal variations registered by the behavior of plants but 

 climate as a composite result of seasons is also shown by the type 

 of vegetation it produces. The index to season has long been 

 the records taken by the meteorologist of temperature, rainfall, 

 sunshine, winds, etc., each one recorded by a separate instrument. 

 Through these records average conditions are ascertained and 

 then the season is measured as it varies from the averages for 

 the different factors. The chief drawback to such a procedure 

 is that each person interested must be familiar with the average 

 figures or have them available for ready reference. He must then 



