BOTANY OF CR01> PLANTS 



where cold or wet weather prevents Uower ()i)eniiig. In 

 India, it has been observed that cross-polh'nation in wheat is 

 more frequent than in northern climates. 



In the wild wheat of Palestine, the kernels 

 are normally retained by the spikelet. It 

 differs also from domesticated wheat in the 

 order of maturity of the spikelets. In do- 

 mesticated wheat, the first spikelets to de- 

 velop flowers are those near the middle of 

 the head, while in the primitive wheat the 

 terminal spikelets are the iirst ones. Primi- 

 tive wheat also shows some indications of 

 sexual dimorphism. Some plants have been 

 observed to bear protogynous, others pro- 

 tandrous, flowers. The spikelets of this wild 

 form never mature more than two grains 

 (Fig. 41), and those of the same spikelet are 

 unequal in size. The smaller grain is borne 

 by the lower flower in the spikelet; this 

 flower has the longer awn too. 



A. Schulz thinks that many, but not all, of the primi- 

 tive wheat individuals found by Aaronsohn are hybrids 

 between T. agilopoidcs Ihaoudar and dicoccoidcs. The 

 Fig. 41. — Spike- origin of the different types of cultivated wheats, as 

 let of wild ernmer given by Schulz, is shown in the following: 

 (Tnticum dicoc- t^- u ■ r i • u -f •; ^ -j • ^1 



cum dicoccoides). '• ^'''koni scnes, of which f. a-gibpoidrs is the 

 X 21.;. prototype. 



2. Emmer scries, of which T. dicoccoidcs is tlic stem 

 form. From this have come dicoccum, durum, lurt^iduiii, and poloiiicum. 



3. SpcU series, of which the stem form is unknown. From this have come 

 spelld, compaclum, wslivuni, and capilalum. 



Environmental Relations. — Wheat is grown under a wide 

 range of temperature conditions. Some varieties come to 

 maturity and yield well as far as 64° N. latitude in Norway, 



