150 The Botanical Gazette. [Marct, 
was and thence to the Esths and Wends where the yew wa 
not found. 
The first step in deciding upon the ancient trade routes is 
to ascertain (1) what plants were used by the cliff dwelling 
Indians, for example, of the Mancas cafion in Colorado, (2) 
to systematically tabulate the distant and local plants and (}) 
to discover, if possible the home of the non-indigenous plants. 
When all of these points are decided upon, we shall have sufi 
cient data with which to map out the Indian trade routes. 
here are several ways by which the plants as used by tit 
cliff dwellers can be determined. (a) By a direct botanical 
determination of the species of plant used. This is possible 
in many cases when we have seeds, nuts, tubers, bulbs, and 
berries used as food; also by a botanical analysis of the pt 
herbs which may have the leaves and flowers preserved. 
examination of the human excrement might disclose by meat 
of the undigested voided seeds, the plants that were used 3 
food. In dealing, however, with the raw materials of mail” 
facture, it is often very difficult to determine from what veg 
etal source they were derived. 6) A microscopic examine 
tion of the plant product will reveal much; for example, ift 
be a piece of wood, its woody characters. We could dettr 
angiosperm or that of a gymnosperm. In case the piece | 
wood shows a gymnospermic structure, it is quite possible b 
use of knowledge already gained to determine whether it be 
yew wood or that of the pine, the fir, the larch and the june | 
A microscopic examination of a dicotyledonous ste 
would also help us in identifying the wood. 
We have a piece of wood before us which we cut in ordef 
to determine its microscopic appearance. A striking featu® 
in such a section is the concentric circle of ducts in the ¢ 
spring growth of wood; in the thick rings sometimes se” 
are two or three rows of ducts, the third one being of small 
size than the others. ‘The first row forms in the spring 
the leaves are opening.” The largest duct is usually ro" 
and 0.13 of an inch in diameter; some are smaller and oe 
flattened or elliptical. Except when first forming these se 
are never open, as usually stated, but are filled with de i aft 
tyloses. Surrounding these ducts are small cells, whit 
termed tracheids, having minute thin places in their 5 
the middle lamella of the cell, however, being not visibly P* 
