THE AMERICAN BOTANIST 33 



In the tropical rain forest, the species retain their leaves, but 

 farther toward the poles, allied species are deciduous. Tropical 

 oaks are evergreen and those of northern regions are deciduous, 

 but even in the latter regions seedling oaks often retain their 

 leaves through the winter. The deciduous habit is very ap- 

 parently an adaptation to avoid the drying effects of the cold. 

 Only in- the drier parts of the tropics do the broad-leaved trees 

 drop their leaves and then it is for the same reason — to avoid 

 injury through drouth. 



Thymol. — Thymol, sometimes called thyme camphor, is 

 distilled from the essential oils of different plants. It is 

 stimulant and antiseptic, and is much valued in medicine for 

 external applications. Formerly the bulk of the product came 

 from Germany and cost about $1.00 a pound, but recent events 

 have sent the price up until it brings eight times as much. In 

 view of the fact that it can be distilled very easily from the 

 essential oils of a number of plants, it is likely that its produc- 

 tion will be taken up in other regions. Thymol, as the name 

 indicates, was originally obtained from the oil of thyme 

 (Thymus vulgaris), but the common horsemint (Monarda 

 punctata) and the wild bergamot (Monarda fistulosa) now 

 contribute to the supply as well as ajowan (Carum copticum). 

 The monardas grow wild in great abundance in many places, 

 and thymol could doubtless be manufactured from them at 

 small cost. Among other plants suggested as possible sources 

 of the raw material are the dittany (Cunila mariana), Basil 

 (Ociniuiu viride and O. gratissimum) , marjoram (Origanum 

 hirtum and O. floribuuda) , and Satureia tJiymbra, a plant 

 related to our summer savory (S. Jwrtensis). In addition to 

 its other uses, thymol has recently been found to be a specific 

 for the hookworm. 



