362 



OHIO EXPERIMENT STATION: BULLETIN 175. 



319 Strong=scented Lettuce (A) *Lactuca virosa L. This lettuce is illus- 

 trated in Fig. 62. This plant has spines or prickles on the midribs and margins of 

 the entire leaves and upon the stem below. Its milky juice, yellow heads of 

 flowers and other characters resemble those of cultivated lettuce. The weed is 

 an introduction, coming to us from Europe and 

 appearing, as to this spe2ies, in Ohio about 1878 or 

 1879. Since that time it has spread to every county 

 of the state and apparently into their most remote 

 corners. This species to northward; in southwest see 

 next. It is a winter annual, starting from seed in 

 the fall and reaching early maturity the succeeding 

 season. It infests clover fields, completely destroying 

 their value and is an omnipresent weed if neglected. 

 Treated of in Bulletin 44 of this Station. Apparently 

 the weed intended to be designated by the term "wild 

 lettuce" in the Ohio weed law. Heretofore confused 

 in specific name; this name, virosa, refers to reputed 

 poisonous character. 



Seeds brown, widening upward, ribbed, 1-8 inch 

 long and about one-third as wide, suddenly contracted 

 into a narrow neck, provided with an abundant 

 pappus and carried long distances by the wind, the Fig. 62. Strong--scented 



chief method of dissemination. Lettuce. 



While this weed cannot now be exterminated it may yet be subdued. 

 If prevented from seeding in most places it will decrease in numbers and 

 aggressiveness. Where mown the plants stool freely and so must be either cut 

 with hoe or pulled to prevent altogether the ripening of seeds. Community of 

 effort will be most effectual in limiting its spread. 



320 Prickly Lettuce (A) *Lactuca Scariola L. This is the sort with lobed 

 leaves, otherwise it resembles the entire-leaved or preceding species. For manv 

 years this one with lobed leaves was very scarce northward, while abundant 

 in the region of Cincinnati. In weedy characters the two belong under the 

 same head. The specific name in this case alludes to the prickles. Seeds like 

 those of the preceding. 



321 Willow Lettuce (A) *Lactuca saligna L. 

 The willow lettuce is a very slender . plant, 

 see Fig. 63, without prickles and with pinnatifid 

 leaves. It was first noted by the writer near 

 Dayton, O., in 1898, being in great abundance to south- 

 ward of that city. Since that time it has become scattered 

 over the western and central parts of the state and perhaps 

 more widely. 



Seeds resembling those of L. virosa but slightly 

 smaller. 



322 Hawksbeard (A) *Crepis tectorum L. This 

 species of hawksbeard together with the biennial sort. 

 has become introduced to spread as a weed. The flowers 

 are yellow while the tall flower-stalk resembles that of fall 

 dandelion. The plants have buoyant, ribbed seeds. 



323 Golden Hawkweed, Orange Hawkweed (P) 

 *Hieiacium aurantiacum L. The cut, after Dr. Vasey,. 

 Fig. 64, shows the characters of this plant. It spreads by 



Fig. 63. Willow Lettuce, runners as well as by seeds. The flowers range from deep 

 orange to flame color. This is a serious field pest, described by Prof. L. R. 

 Jones as unquestionably the worst of recent invaders in Vermont. It has 



