62 THE JOURNAL OF BOTANY 
Der pes ig der Pflanzen. By Prof. J. Wimsner. Pp. 322, 
© Illustrations. Leipzig: Engelmann. 1907. 
For many years practical men have paid more attention than 
bistuniokirt to the effect of light upon the whole life of a plant. 
horticulturist has long recognized that certain plants thrive best 
in shady spots, while others flourish only in well-lighted situa- 
tions. Foresters, too, have classified trees into tii -demanding,” 
‘“shade-enduring’”’ (and even ‘“shade-demanding”’) species, and 
have appreciated the fact that in different ee the amount of 
light required by a species varies. Furthermore, gardeners have 
spec 
practically appreciated that it is often necessary to grow tropical 
plants at higher temperatures in ee ee than in the tropics, 
ee because in o@ former the light is weaker than in the 
tte et in none these cases have we been justified in 
assuming that the aster is purely one of hear se for it is 
obvious that with variations in the intensity and duration of light 
te or — German word the English equivalent ‘photic ration 
proposed, and since then Wiesner has suggested the term 
ch he m tion of the full intensity of daylight 
which is falling upon a plant—and absolute photolepsy—by which 
he means its absolute intensi By ns of actual measurements 
mea. al m 
the vague terms “ sunplant,”’ « i sharma ” and the like, are thus 
replaced by statistical information 
es, i 
sg account of the illumination of argh photolepsy in rela- 
foliation and to mycorhiza : the prec nt of green of leaves ; a 
physiological oe of Saco: : sera in relation to 
With the caste output of new gee botanical science 
will be increasingly ee upon the e of igrrerteenree 
— of this kind. ae 3 t Ss free from ri qaeliie lengt 
undancy that are so unf ch 
sharia Gertnat ak coe = ortunate a feature of cad 
Percy Groom. 
