KEY TO FAMILIES OP ENDOGEN WEEDS. 45 



sarily brief, it is more than probable that some of the characters 

 given will not agree with the plant in hand. All plants vary more 

 or less, no two individuals being exactly alike. If the most of the 

 more important characters agree it is very probable that the plant 

 has been correctly traced. 



All of the weeds listed belong to the sub-kingdom of plants 

 known as Spermatophyta or seed-bearing plants in which the pol- 

 len grains develop into poll en* tubes which find their way to embryo 

 sacs in ovules and there fertilize the germ cells or microscopic eggs, 

 which remain enclosed in the ovules until they ripen into seeds. 

 All of them also belong to the class Angiospermce or flowering- 

 plants in which the ovules are enclosed in an ovary which becomes 

 the fruit. 



KEY TO SUBCLASSES OF ANGIOSPERM^. 



tt. Leaves with parallel veins, mostly alternate, entire, linear or grass- 

 like and sheathing the stem at base; stem without distinct layers 

 of bark, wood and pith; embryo of the seeds with one seed-leaf, 

 the first leaves of the sprouting plant alternate ; parts of the flowers 

 usually in 3's or 6's. ENDOGENS, p. 45. 



aa. Leaves with netted veins ; stems formed of circular rings of bark, wood 

 and pith ; embryo and young plant with a pair of opposite seed- 

 leaves ; parts of the flowers rarely in 3's or 6's. EXOGENS, p. 46. 



KEY TO THE FAMILIES OF ENDOGEN WEEDS.* 



a. Ovaries simple, distinct, 1-celled, 1-seeded, formed of a single carpel ; 



flowers without sepals or petals, borne in the axils of dry chaffy 



scales (glumes) and arranged in spikes or spikelets. 



6. Stems (culms) mostly hollow, cylindrical; sheaths split to the base; 



glumes in pairs; fruit a grain. GRASS FAMILY, p. 50. 



&&. Stems solid, often triangular; sheaths closed; glumes single; fruit 



an achene. SEDGE FAMILY, p. 57. 



aa. Ovaries compound, formed of 2 or more carpels; flowers complete, 



their parts in 3's or 6's. 



c. Sepals and petals (perianth) green or brown; stems rush-like with 

 grass-like leaves; flowers small (stamens 6 and leaves all basal 

 in our weeds.) RUSH FAMILY, p. 59. 



cc. Petals or inner part of the perianth colored ; fruit a 3-celled capsule 

 splitting down the back of each carpel ; plants mostly springing 

 from bulbs ; our weeds with an onion-like odor. 



LILY FAMILY, p. 60. 



*The keys aa given include only the families to which the weeds hereafter listed belong. 



