230 



phenomenon is n(jt due to phosphorus but to oxidation in con- 

 nection with certain fungi and bacteria. 



The lecture was ilhistrated by about thirty lantern shdes that 

 showed the topographic features of the region, the location of the 

 ditches and other waterways, the characteristic vegetation, etc., 

 mostly made from photographs taken by the lecturer in the 

 course of a two days' trip from one side of the swamp to the 

 other. 



Arthur Holltck. 



AUTUMN COLORS^ 



This lecture is given at The New York Botanical Garden each 

 year during the season of autumnal colorations. Numerous beau- 

 tifully colored lantern-slides have been made especially for use 

 in this lecture. Some of these show general scenic or mass 

 effects, others show the colorations that are characteristic of indi- 

 vidual species which grow wild about New York City or are 

 introduced in culture, and others show particular features in the 

 development of the colors. Altogether they are representative 

 of the views of autumn and of the various types of autumn 

 colorings. 



The main colors of the foliage of plants in autumn are red, 

 yellow, and brown in various shades and intensities, with rarely 

 white. Combinations of two of these give many intermediate 

 shades. 



In discussing the how and why of autumn colorations, it is to 

 be noted that the color clianges are associated with the death and 

 fall of leaves. This is in general a response to the approach of 

 unfavorable conditions, or as we often state it, a preparation for 

 winter. The leaves of the ordinary deciduous trees, which yield 

 our most noticeable colorations, are rather tender organs. They 

 grow rapidly, they contain much soft ]>ulpy tissue, and they die 

 quickly when dried out or when frozen. They are weak parts of 

 a plant when unfavorable conditions approach. Thus, with the 

 coming of autumn the activity ot tlir leaves ceases, they begin to 

 die, and the food materials in tliem iwv transferred into the sum. 



1 Alistracl of an illiisltatid Itctiiii' K'vin in tlic Mnsruni Huilding of 

 The New York I'.i>tanical riar<lrii, Saturday afkMiiooii. October lo. 1925. 



