INTRODUCTION AND METHODS. 13 



threads are used to mark divisions sufficiently small to permit following 

 the florets with accuracy. 



Visits are regularly made once each day, except during the rapid develop- 

 ment of the warmest days, when morning and afternoon visits are often 

 necessary. Once or twice during each series, records are taken in the early 

 morning, at noon, and in the evening in order to obtain the finest details 

 in the changes. Similarly, one or two visits at sunrise and sunset are 

 necessary to determine the times of opening and closing of many species. 

 The regular visit is made in the morning, preferably at the same hour, 

 though this must often be modified as a result of weather or by other duties. 

 The use of two persons, one to observe and the other to record, effects a 

 great saving of time, but when this is impossible, the entire record should 

 be made by the same individual. The record sheet for each species is 

 ruled to hold the entries for 20 flowers, extra sheets being employed when 

 all the flowers of a head or umbel are to be taken into account. The same 

 form is used for both the field and the final typewritten record and an 

 endeavor is made to enter the observations so that the field sheet can be 

 copied directly. This necessitates a fixed set of abbreviations in order to 

 save both time and space. The entries for each visit are made beneath 

 the preceding one, the space being left blank when no change has occurred, 

 as this permits ready comparison with the last condition. The date and 

 the hour are entered in the first column for each species, the round of visits 

 always being made in the same order to allow the same interval, especially 

 when two or three visits are made in one day. A record is kept of periods 

 of cloudiness and rain, in addition to the usual records of temperature and 

 humidity. The striking differences in the rate of floral development in 

 sun and shade ecads of the same species have been the subject of a special 

 study, in which temperature and humidity were also determined under 

 the forest canopy. 



Life-history record of a representative species. — The detailed life- 

 histories have been recorded for about 100 species of the Pike's Peak region. 

 For the majority of these this was first done in the summer of 1912 and has 

 been repeated in 1921 and 1922, two simultaneous sets of readings being 

 taken in 1921 by different observers. Because of the limitations of space, 

 the detailed table (table 1) is given for a single species only, and this is 

 restricted to 10 flowers on two different plants, taken from the 1921 observa- 

 tions. The main features of the life-history of 26 species are illustrated 

 in plates 2 to 14, and the stages described in the corresponding legends. 



