322 BROOKLYN BOTANIC GARDEN MEMOIRS 



summer, when compared from year to year, are as exact in relation to 

 time and energy expenditure as are the flowering periods. Thus, if 

 we compare the vegetative growth of the Yellow Adder's Tongue during 

 1913 with that of the present year the tips of the leaves were simul- 

 taneously emerging from the ground over wide areas of a valley on 

 March 27, while this year they appeared on the nth of April. In 

 both cases these leaves were 2| inches high 3 days thereafter, and so 

 comparatively suddenly transformed wide woodland areas from a 

 bare unclothed aspect into rich showy brown-green verdure. 



If we consider now a few naked eye details that depend on definite 

 histological changes, it may be said that botanists are aware that for 

 any given species of shrub or tree a fairly definite period arrives 

 when easing and separation of the epidermis along the stem is effected, 

 after cork formation has replaced it functionally. Some species show 

 this change in the latter part of the first year, many in the early part 

 of the second, while others may be delayed until the following autumn 

 or even later. A more pronounced though related occurrence is seen 

 annually in the oriental plane. The extensive flakes of old dull-gray 

 cork start to separate synchronously on the average about June 28 

 and so reveal the white younger cork underneath with increasing 

 effect during the next few days, but variation as to date of this event 

 may occur from year to year according to environal stimuli. Oppor- 

 tunity has twice occurred for comparing this with the behavior of the 

 same species round Kew Gardens, England, and there a like change 

 starts on July 29. This comparative result agrees closely with other 

 data obtained as to floral maturation. 



Closely related again to the above studies is one that has scarcely 

 been touched in this country, but which has been investigated by 

 Hoffmann-Ihne in their observations at Giessen. This is an exact 

 comparison of flowering periods according to longitude and latitude, 

 particularly the former. Exceptional facilities exist for the prose- 

 cution of such an inquiry in this country, for were thirty or forty 

 observational stations established under competent workers, and the 

 whole correlated at a central office, valuable results would accrue after 

 a period of ten to twelve years. A feature of interest here is that a 

 considerable number of plants of the eastern seaboard extend their 

 range from central or northern Florida to Newfoundland or even 

 Labrador. One of these which the writer has shortly referred to 

 elsewhere^ is our native pitcher plant (Sarracenia purpurea). In 

 northern Florida, as for example round Ponce de Leon, it starts to 

 bloom in the last week of March and continues until April 10. In the 

 Charleston region, as at Summerville, it is averagely five days later; 



^ Engler's Pflanzenreich, \'ol. 4 (1908), p. 23. 



