i88 
continued for 24 hours, or any other number of degrees for an 
inversely proportional number of hours.” 
When the temperature during any period remains either above 
or below the base temperature, the difference between the base and 
the mean temperature gives, approximately, the accumulated tem- 
perature. 
A note being kept from the beginning of the year, day by day, 
of this accumulated temperature, and the day-degrees below 42 0 
deducted from those above it, it will be found that a definite 
number of day-degrees in excess is needed for the flowering and 
ripening of each kind of plant. It is of advantage when these 
phytological observations are made by the same person and on the 
same plants from year to year. The plants selected should not be 
in a very sheltered situation nor, on the other hand, in too exposed 
a position. “A plant is to be considered” in flower “when the 
stamens on the first blossoms on it first become visible.” In other 
cases when either the stigma is mature or the anthers burst. In 
the case of the Hazel the fertile flowers are to be observed. The 
“first flowering” observations mean, of course, those of the 
blossoms produced from the ordinary growth of the current season. 
ERRATA. 
Page 6 , for R. Sardous read R. sardous. 
Page 6, for R. hirsutus read R. hirsutus. 
Page 52, for P. malus read P. Malus. 
Page 125, under the figure of the Yew, for Toxus read Taxus. 
Page 126, under the figure of the Birds-nest Orchid, for N. Nidus-airs 
read N. Nidus-avis. 
Page 131. The line Allium ( L .) Garlic should be placed above A. Ampelo- 
prasum. 
