MORPHOLOGY OF THE BAELEY GRAIN. 5 



DEVELOPMENT OF THE BARLEY GRAIN. 



An understanding of the office and behavior of the various organs 

 of the barley grain is greatly facilitated by observations upon their 

 origin and development. Some of these organs are functional 

 thi'oughout the existence of the seed; others important in the early 

 stages afterwards disappear, while still others become so modified 

 as to be serviceable in a totally different way. 



The flower of the barley plant is inclosed within the flowering 

 glumes, as m all gi'asses. It consists of a simple ovary containing a 

 single ovide. The stigma is two branched and plumose. Three 

 versatile anthers attached below the ovary fit into as many natural 

 angles in the glumes. On the dorsal side of the ovary are two 

 lodicules. 



At the time of flowering, the ovary wall is a but slightly modified 

 vegetative structure. It consists of the usual epidermis, a colorless 

 parench^^na of several layers, a cMorophyU-bearing parenchyma, and 

 an inner epidermis. The cldoi-opliyll layer is the only one in any 

 way exceptional. The ceUs of this lie with their long axes at right 

 angles to that of the others and tangential to the grain. Inside the 

 ovary are two integuments which probably act as conductive tis- 

 sues to the gi'owing poUen tube during fertilization. Each is formed 

 of two layers of thin-walled ceUs. The cells of the outer integument 

 are somewhat larger than those of the inner one and are much thin- 

 ner walled. The contrast between the two integuments is very 

 evident in Plate I. Inclosed by the two integuments is the nucellus, 

 which is in turn surrounded by its own investing membrane, con- 

 sisting of a single layer of cells. In the parenchyma mass of the 

 nuceUus is the embryo sac, which before fertilization contains the 

 usual ( ight cells. At this stage of development the cells of all the 

 tissues are filled with phisma. 



After fertilization the ovary increases in length and width. As 

 the essential parts of the developing seed arc taking shape, certain 

 now useless portions of the enveloping structures become modified 

 and in some cases absorlx'd. The plasma gradually disappears from 

 the cells of the outer integument, the cell walls become transparent, 

 and finally dissolve and disappear. The inner epidermis is also 

 absorbed, although not always completely, as traces som(>times p(T- 

 sist at matin-ity. A little later, portions of the ovary wall begin to 

 weaken. The starting point is usually just outside* the chlor()])hylI 

 layer, and the j)roc(!ss advances outward tlu'ough the overlying 

 parerifhynui layers. At maturity this tissue is rej)i'(>sente(l by a 

 compressed mass of almost disconnected cells, hi the earlier stages 

 of growth it is this reduflioti of tissue thiit establishes I be ^'gicen 

 ripeness" of Kudelka, llic nMiioxid of ijic overlying cells bi-iu;.;ing 

 the chioropliyll l;i\-ei' neiij-er 1,() ibe surface, lhus inlensifyiug the 



