CHAPTER XIV. 

 DESCRIPTIONS OF SOME COMMON WEEDS 



The More Important Families of Weeds. The weeds 

 described in the following pages are quite widely dis- 

 tributed. Many of them are as common in New England 

 as in the Northern Mississippi valley and many of them 

 are common on the Pacific coast. Some weeds are local, 

 such as the tarweed of California. Those who are 

 especially interested in a further study of the various 

 regions should consult some of the manuals and floras, 

 such as Robinson and Fernald, Gray's "New Manual of 

 Botany" and Britton's "Manual of Northeastern United 

 States." 



KEYS TO FAMILIES 



1. Plants producing spores, in spore cases or sporangia. 



Rushlike and jointed (Equisetaceae). P. 138. 

 Not rushlike nor jointed (Polypodiaceae). P. 137. 

 Plants producing pollen and ovules, which develop into seeds. 2 



2. Embryo of one cotyledon ; stem endogenous with no distinc- 



tion between pith wood and bark; leaves generally par- 

 allel veined (Monocotyledoneae) 3 



Embryo usually with two cotyledons; stems with distinct wood 

 pith and bark; leaves netted veined (Dicotyledoneae) 6 



3. Flowers with small bracts or scales 4 



Flowers with a perianth, petal-like, and having parts colored 



alike (Liliaceae). P. 159. 



4. Scale i (Cyperaceae). P. 157. 



Scales more than one : 5 



5. Scales in pairs (Gramineae). P. 139. 



Perianth of six similar scales (Juncaceae). P. 158. 



6. Petals absent 7 



Petals present 12 



7. Flowers monoecious, dioecious or polygamous. 



Fruit, a three-lobed, three-seeded capsule. Plants with 



milky juice (Euphorblaceae). P. 193. 

 Fruit, one-seeded (Urticaceae), P. 160. 



8. Fruit, not an achenej fleshy plants with a coiled embryo 9 



Fruit, an achene. 



135 



