TRITICUM 109 



is returned as shorts, middlings and bran. The composition 

 of these varies somewhat with the milling process. 



Germination of Wheat. — The time required for germina- 

 tion depends upon external conditions. The optimum tem- 

 perature for the germination of wheat is close to 84°F., the 

 niinimum 40° to 43°F., and the maximum io8°F. Germina- 

 tion will take place under field conditions usually within 

 from four to ten days. Nobbe finds that wheat will 

 begin to germinate in one and three-fourth days at 

 65°F., two days at 6o°F., three days at So°F., and six days 

 at 4o°F. 



Three germinating stages in wheat are shown in Fig. 2. 

 The primary root is the first to appear. It ruptures the 

 coleorhiza which remains as a collar about the root where it 

 breaks through the grain coats. Very soon two lateral roots 

 appear; hence the primary root system consists of a whorl 

 of three roots. The growing point elongates, the first young 

 leaf being enclosed by the leaf sheath or coleoptile, a closed 

 and pointed organ. The coleoptile protects the growing 

 point and serves as a boring organ. The coleoptile of wheat 

 has the greatest soil-penetrating ability of the common 

 cereals. Its length varies with the variety and with the 

 depth of seeding. The closed end of the coleoptile is 

 broken by the first foliage leaf. The cotyledon (scutellum) 

 is left beneath the ground. 



Repeated Germination. — The grains of wheat, and the seeds 

 of a number of other agricultural plants, are capable of 

 repeated germination. A grain may start to sprout, the 

 process be stopped by dryness, and sprout again if moisture 

 is available. Beal germinated wheat and buckwheat six 

 times, each time allowing the root and stem to grow to the 

 length of the grain, with the following results: 



