336 Meyen’s Report for 1839 on Physiological Botany. 
the case of marks made on those trees in forests which are 
destined to be sold. 
M. C. van Hall* has laid before the Academy of Sciences of 
Amsterdam a series of observations on the increase of trees in 
thickness, by which it is clearly shown which trees thicken 
slower or faster, and what is the proportion of increase in 
different ages, different years, and even in the several months. 
An oak stem which in 1826 had a circumference of 140 mil- 
limetrest, during ten years increased yearly on the average 
37 mill. in circumference ; an oak of 555 mill. increased during 
ten years 307 mill., or yearly 30; mill.; and another of 1792 
mill. in circumference increased yearly only 123 mill. Anelm 
of 170 mill. increased yearly on the average 36,5, mill.; an- 
other of 190 mill. 323; and one of 1155 mill. only 202 mill. 
A willow (Salix alba) of a circumference of 191 mill. increased 
474 mill., and one of 1130 nearly as much. The Canadian 
poplar (Populus monilifera), in circumference 620 mill., in- 
creased yearly as much as 81 mill.; and one of 1645 mill. 
even 91} mill. Birch and maple, on the contrary, increased 
even when young only about 10 or 12 mill. Pinus Abies, Tilia 
europea, Juglans regia, and Aisculus Hippocastanum were 
measured in the same manner. Moreover, seven different 
kinds of trees were measured for five years during the 
summer monthly, and these measurements in particular 
have given good results. It appears, first of all, that the 
increase in the five years was not always the same, and that 
no determinate increase or decrease therein, according to the 
age, could be observed. The increase of the circumference 
varied very much in the different months of the several years, 
which is evidently tobe referred to the weather. We will here 
give only one of the tables in order to prove the above state- 
ments. A stem of Ulmus campestris measured in February 
1834 265 millimetres, and increased in millimetres 
May. June. July. Aug. Sept. Oct. Total. 
1834 cecove AO Sees Zh e8apes LF Gaseny ARP: coeds Y ee pS ee ae 693 
BDU ocenss i Repro ED stipes hi peer 56 Wisse ‘Bar ohs x Teacuge 50 
T8356 2.2.35 DO ahavee Li fides OG senkee LO as sens Ti pyipes Or oelnan 53 
SRT: sogna’ Di Silee ve Cidtisks a7 theses pate tee 2) egedds O lots 46 
1838 ...... Bo asepss Es Bae Shae 1G © anes 12 seccee 4® iscvark ee 544 
M. van Hall remarks, that by the observations, the opinion 
of Agardh, that trees increase in length in the first part of 
the summer and in breadth in the latter part, is proved to be 
unfounded ; and that they also show that the circumference 
of stems is not altered during the six winter months. 
[To be continued. ] 
* Waarnemingen over de Toeneming der Boomen in Dikte.—Tijdschrift 
voor Natuurl. Geschied. en Phys. 1839, vi. p. 207. 
+ The millimetre is 03937 of an English inch. 
