230 PLANT ANATOMY, 
reserve substances. Starch is, therefore, often found in them, 
especially in winter (Quercus). 
Fie, 147.—Sieve-tubes from Fructus Papaveris (Dippel). 
In older stems and branches, the heart-wood (duramen) and 
Sap-wood (alburnum) may be distinguished. The heart-wood, 
Fre. 148.—Sieve-tubes of Acer. (a) more feebly, (b) more highly magnified. a, 
Sieve-plate on a transverse section; e, the same as se2n from the surface; p, the con- 
tracted plasmatic contents of the sieve-tubes (Hartig). 
which is mostly characterized by a darker color (logwood, red- 
wood, and other varieties of dye-woods, Guaiac), consists of the 
