225 



of both heat and moisture, in which case all annual periodicity dis- 

 appears and the plant goes through its cycle of vegetation independ- 

 ent of the months of the year, as in the warm and rainy regions of 

 Java. 



As before said, the absolute value of the ratio f/w need not be 

 considered at present, and in fact it changes with the units of time, 

 of temperature, or rainfall, etc. Linsser divides the depth of the 

 monthly rainfall, expressed in Paris or French lines, by the average 

 temperatures of the respective months expressed in degrees Centi- 

 grade. 



In order to ascertain which of his European stations lies in the 

 zone A and which in the zone B it is necessary to adopt some limit- 

 ing value for the ratio /Ai', and to this end Linsser examines these 

 latios in connection with the phenomena of plant life, adopting the 

 principle that as two plants from different places, accustomed to 

 different quantities of heat, behave differently when they both receive 

 the same quantity of heat, so also two plants from places having dif- 

 ferent distributions of rain will behave differently and arrive at the 

 same phase at different times when they are brought into the same 

 place or under the same local climatic influences as to moisture and 

 temjjerature. 



In order to decide as to the limiting value Linsser studies the 

 I'atios for the hottest months of the year, which all relate to the 

 ripening phases of vegetation, and finds that for the units of measure 

 adopted b}" him the value of ratio f^'W^ that rej)resents approximately 

 a dividing line between the stations that have an abundance of rain 

 in summer relative to the summer heat and those that have little rain 

 relative to the heat, is 1.2. I have indicated in the preceding table 

 by the letters A and B the stations that have //i«>1.2 and /Ay<1.2, 

 and which Linsser puts into his zones of abundant and scanty sum- 

 mer rains, respectivel3\ 



I give in the following table some of the more striking and perma- 

 nenth^ important results of Linsser's computations. Plis original 

 work, based on about 30,000 observations, gives for each of his 31 sta- 

 tions and for 118 species of plants and for each of the three phases — 

 leafing, blossoming, and ripening — the ordinary phenological con- 

 stant or sum total of mean daily temperatures above 0° C., and also 

 his own physiological constant, which is the ratio of this sum total 

 to the annual sum total for the station. In the following summary 

 I give the physiological constant as it results from the average of 

 all the individual stations in the zone A ; but for the sake of quicker 

 comparison between the results for zones A and B the summary gives 

 not the physiological constant for B, but its departure or difference 

 2667—05 M 15 



