Rural School Lelvflet. 659 



(a) The shell and its pores, (b) The two shell membranes turned 

 back from the shell, (c) The air space, (d) The three layers of albu- 

 men, (e) The vitelline membrane surrounding the yolk, (f) The 

 vitellus contained within the vitelline mambrane. (g) The white yolk 

 and the dark yolk showing its concentric layers, (h) The germinal disc, 

 (i) The chalaza ("hammock cords"). 



Definitions. 



Vitelline membrane. — A delicate film-like skin, which encloses the 

 liquid portion of the yolk of the egg. 



Vitellus. — The yellowish-like substance within the yolk of an egg — 

 closed by the vitelline membrane. 



Embryo — The young chick in the first stages of development, before 

 it leaves the shell. 



Concentric layers. — Thin layers of yolk substance of different shades 

 appearing to be arranged in rings, one within the other, whichever way 

 the yolk of a hard boiled egg is divided. 



Incubation. — The process of development of a chick within the egg, 

 requiring heat, moisture and air. 



Chalaza. — A twisted band of thickened albuminous substance (white 

 of egg) to be found attached to the yolk for the purpose of keeping it 

 properly suspended. 



Shell membrane. — Two thin skin-like tissues which line the inside sur- 

 face of the shell of the egg. 



Germinal vesicle, germinal spot, germinal disc. — The part of the yolk 

 of an egg undergoing incubation, which contains the first traces of the 

 developing chick. 



LESSON IV. THE PEA FA^IILY. Figs. 6, 7, 8. 

 By G. F. Warren. 



Object. — To learn to recognize leguminous plants. 



Materials.— One or more hand lenses, bean 

 or pea blossoms and pods, clover blossoms, 

 and as many other legumes as possible. (See 

 Rural School Leaflet for September, p. 7.) 



The group of plants that is most import- 

 ant to mankind is the great grass family 

 (Graminecc) which includes corn, wheat, oats, 

 rve, barley, timothy, and others. One will^^c- 6--i'^« ^ozver cut in two. 



,., ,, , 1, ,, , ,-, I, a sepal; 2. standard or banner 



readilv see that all these are much alike, par- (one of the petals); 3. keel 



,',.,,, . , r , (part of the corolla); 4, style; 



ticulaiiy in the leaves and leaf arrangement, s, stamens. 



The second group in importance is the pea family {Legumifio sees'). 

 These plants are commonly called legumes, or, more properly, leguminous 



