72 
habiting- the outer layers of the root, secure the necessary 
mcjisture and thus obviate the necessity for root hairs. E. 
Transeau reports in the January Botanical Gazette that 
in stutlyinj::^ certain bogs in the Huron River valley he found 
a long- list of plants witli mycorliiza, as this root-fungus 
is called, among u-iiich may be mentioned the larch {Lari.r 
Americana), white pine { Finns strobus) , the black spruce 
^Picca Mariana), yellow birch { Bcfala Icnta), dwarf birch 
\B. puauia). the cranberries { l-'acciniiini o.vyoccns) and 
i\ Macrocrarhon i,the running h\xch(Chio genes Jiispidula) . 
the blue berry i raeeimnii eorymbosuni) and (Greenland tea 
( Lediiia latifoliuui) . Experiments seem to indicate that 
these mycorhiza develop oulv when there is not suliicietit 
air in the soil. 
\- .VMS.— In the United Slates there is considerable liazi- 
ne>> as to :hf detinit'on of the word _\am. By many the com- 
mon .vveet potato of the South is so called, but this is a mis- 
take. There are no yams grown in this country, unless a 
tew specimens may ]>e cultivated in Florida. It would be 
m^corrcct, however, to say triat no yam species grow in the 
-^(hble ST) 
sidered an edible plar 
the Ameri 
apparently }>el(Hig lo t!,e .pecie. n.amed D. alta. 
named varieties are cultivated that mav be referred to (,ne 
or another of these fo-ur species. The part eaten is the 
underground rootstock wliich in some forms reaches a length 
tour tcet ajil a diameter of eigfiteen inches. One does 
not ordinarily g(j to. market for yams, or ever^ for a yam. 
but f<.r aj,iece . f yam. There is great difference in the flesh 
ot the ditterent : arietie. of yams. s<-,me being soft and white, 
whde c;thers are coarser and yellowish in color. All the 
plants {)ear a general resemblance to our common wild 
species. 
