MISSOURI BOTANICAL GARDEN BULLETIN 83 
Various preparations, such as mud spray, lime and salt 
spray, whitening, ete., all of which were costly and unsat- 
isfactory as well as unsightly, have been tried for shading 
the greenhouses at the Garden. Until recently the formula 
used was: white lead, whiting, and shutter green, mixed 
with benzine to form a spray. The use of this preparation 
required over 300 gallons of benzine annually to cover the 
entire glass area, and the spray was both costly and un- 
pleasant to apply. Frequently too much white lead would 
be used or the solution would not be sufficiently agitated and 
permanent splotches would result which it was necessary to 
scrape off for the winter season. Recent experiments have 
resulted in a much cheaper and more satisfactory spray 
which will withstand heavy rainy periods but nevertheless 
will wash off by fall. Water is used instead of benzine and 
potassium bichromate and powdered glue are substituted for 
white lead. The following is the formula used, the shutter 
green being omitted if a white shade is desired: 
bf AC ee ee Ce ae 1 gallon 
bk Ch os: ): RO a nae eee 1 pound 
POOR WRCCH COG yo sics cidsdocccanoaeomeneenan 214 ounces 
Powdered glue chic Be emcee 3 ounces 
Bichromate of potassium 1% ounces 
In preparation, the powdered glue and the potassium 
bichromate are dissolved by boiling in separate containers. 
The whiting is dissolved in cold water. The glue and 
bichromate of potassium should not be mixed with the water 
and whiting until just before using, and after mixing the 
solution should be kept from the sun to prevent premature 
setting or hardening. This solution, after screening, will 
pass readily through a hand spray or barrel pump. At the 
Garden the small hand syringe is used in applying the spray 
to the small houses, and if a sharp jerky movement is used 
an even shade will result, but the ordinary movement pro- 
duces an irregular shade. In spraying the large conservya- 
tories the power spray supplied with Bordeaux nozzle is used 
to advantage. 
