IOWA acadj:my of sciences. 47 



and tabulations might be made. I think it is fortunate that the Weather 

 Bureau of the Department of Agriculture is undertaking tliis work and that 

 Prof. Bailey is to bring together some of the scattered information on this 

 subject. 



But before any accurate phamological maps can be made it will be neces- 

 sary to carry on these observations much farther than they have been carried. 

 The published records, so far as I have looked them up only occur in New 

 York, Wisconsin, Michigan, and Iowa.' It would no doubt aid systematic 

 botanists somewhat if a phtonological map could be prepared for the United 

 States as HoiTman- has for Central Europe. If these records are to be of great 

 value they must be taken with some care. Everyone is familiar with the in- 

 dividual differences to be found in some plants. Caspai-y-' has called attention 

 to the gx-eat variation of the time of flowering of certain plants in limited 

 areas. This difference iu the opening of ffowers may be carried beyond the 

 average period not only several days but as much as two weeks. Magnus ^ 

 states that Juglans regia flowers seventeen days earlier in the closely 

 crowded parts of Berlin than in the suburbs. This early flowering, he thinks, 

 is not due to an individuality of the tree, but to the great amount of heat 

 that is radiated by the numerous buildings. But many of these differences 

 are individual variations of the tree or certain peculiarities of the soil. The 

 writer has often observed great differences in the time of leafing and fall 

 of leaves in trees and shrubs growing in close proximity. In the autumn 

 of 1891 the writer had under observation several trees of the Soft Maple 

 (Acer sacchariniim) . The trees covered an area of not more than 900 square 

 feet, yet the leaves began to turn yellow and lose their foliage at very dif- 

 ferent times. One tree was fully ten days later than the earliest one. 

 The appearance of leaves of different individuals of this species is a matter 

 of common observation. 



In 1883 I made some observations on the leafing of different individuals of 

 Shell Bark Hickory [Hicoria ovata) and Stag-horn Sumach (Rhus typhina), 

 which were reported by Prof. Trelease.^ Individuals of these species 

 showed considerable difference in the appearance of their first leaves. In 

 part due to exposure and soil conditions no doubt, but part may have been 

 an individual peculiarity. In making phamological observations it is of 

 course important to select an average tree or specimen. Prof. Baileys has 

 well said " While the method gives us the characteristic of the individual 

 rather than of the species, it is, nevertheless invaluable from the fact that it 

 eleminates all variations due to soil and exposure; and the writer is confident, 



iBrittou, Hull. Torrey Bot. Club Vol. VI No. 42. p. 235. 



Leggett " " '• •' •' " 44, p. 22J. 



Trelease first and second annual report Wis. Agrl. Experimental Station. 



Halsted, Bull. Iowa Agrl. College, Ueptof Bot. 1886, p. 42. 



Bailey, Bull. No. ai, Michigan Agrl. College, p. 67. 



Beal & Wheeler, Flora of Mich. 



Pammel, Bull. Torrey Bot. Club Vol. XIX, p. 375. 



aPetermauu'Geogr. Aliih. Vol. XXVll, pp. J9-26, two plates. Just. Bot. Jarhesb, 

 1881, p. 290. 



sUeber die zeiten des aufbrechens der ersten Bliithe , KOnlgsberg 1 Pr. Sehrlf- 

 ten der Physilv-Oel<on. Gesellsch. zu Kouigsberg, Vol. " ^1^^' l**^-> llo-126. Just. Bot 

 Jarhesb. Is82, p. 26!». X-^ 



* Monatschr. d. Vereins zur Beford. des Gartenbaues der Konlgl. Preuss. Staatens, 

 24 Jahrgang, 1881, pp. 204-205. Just Bot. Jarhs., 1881, p. 291. 



5 First annual report of Wisconsin Agrl. Exp. Station, p 56. 



6 Bailey, Bull. No. 31, Agrl. College Mich. 1887, p. 67. 



