224 BOTANICAL GAZETTE [SEPTEMBER 
Counting or measuring the stomata im situ on the leaf is possible with a 
few plants, notably Begonia coccinea, Chrysanthemum frutescens, Fuchsia 
speciosa, Impatiens Sultani, Primula obconica, Pelargonium zonale, Trades- 
cantia zebrina, and Vicia Faba. In some others the condition of the pore 
can thus be observed, though the outlines of the guard cells are not clear: 
this is true in Senecio Petasitis, Helianthus annuus, Cyclamen latijolium, 
Coleus Blumei, Cestrum elegans, and Phaseolus vulgaris. 
Marked variations in number and size of stomata occur, not only in 
different varieties of the same species, but in the same varieties grown 
under different external conditions. So far as my observation goes, 
however, the variation is greater in number than in size. Furthermore, 
while in most leaves the stomata are fairly evenly distributed over the 
surfaces containing them, in some, especially in oblong leaves (€. g-, Fuchsia 
speciosa, Helianthus annuus, and Impatiens Sultani), the stomata are much 
more numerous near the base than near the tip (more than twice as many), 
and near the midrib than near the margin. For this reason very different 
figures might be given for the same leaf by different observers. 
The opening and closing of the stomata of greenhouse plants is corre- 
lated closely with the time of day, and secondarily with the weather. 
already noted, they are, as a rule, as wide open as they can be about 104 “et 
—this, of course, in well-watered plants. In favorable weather they remain 
wide open until about 2.30 Pp. M., when they begin to close, and they are 
mostly completely closed by 5 Pp. M., though some may remain open until 
6. On hot days in the spring they may close as early as 12 M., probably 
because of incipient wilting of the leaf. If the stomata are closed by 
wilting, they may be made to open, partially at least, by immersion of 
leaf in water. - 
The best plants for general laboratory study, taking account of eo 
removing the epidermis, size and clearness of <tomata, and commonness 
occurrence in greenhouses, are, in order of excellence, Chrysanthemum 
jrutescens, Tradescantia zebrina, Pelargonium zonale, Fuchsia spect0st 
Helianthus annuus, and Vicia Faba—SoPHia H. EcKeRsoN, Smith COME 
Northampton, Mass. 
THE ABSORPTIVE POWER OF A CULTIVATED SOIL 
(WITH THREE FIGURES) 
In the winter of 1908 we undertook a study of the absorptive pone 
certain soil from one of the fields of the Michigan Agricultural if vely 
addition to the purely analytical methods which have been mance 
employed up to the present time in investigations of this kind, it was d 
of a 
In 
