434 SCIENCE PROGRESS 



"The degree of union is such that one cannot even state 

 with certainty where the epidermis of the nutrient root ceases 

 and that of the Broomrape begins. The latter looks as if it 

 were a branch growing out of the root it preys upon and this 

 apparent fusion gave some colour to the view of the earlier 

 botanists, who, ignorant of the life-history of these parasites, 

 believed that they did not arise from seeds but were patho- 

 logical outgrowths from the roots produced from their tainted 

 juices ; in other words, that they were ' pseudmorphs ' sprouting 

 from diseased roots in the place of leafy branches." 



Happily the Broomrapes rarely occur in sufficient numbers 

 to do much damage agriculturally ; they are of interest chiefly 

 on account of their peculiar appearance and mode of living. As 

 no green leaves are produced, the plant is thrown back upon 

 a parasitic life for its very existence. As so often happens with 

 weed plants, the seeds retain their vitality during long periods. 

 Experiments have been made 1 to test the vitality of the seeds 

 of another species of Broomrape {Orobanche crenata) by carrying 

 on germination tests in pots during a period of fourteen years ; 

 •.hese have shown that the seeds lose practically all germinative 

 ability after being eight years in the soil. 



Weeds of Special Interest 



Twitch or Couch. — Some of the most familiar words used in 

 connection with agricultural weeds are " Twitch " and " Couch " 

 but farmers will give curiously contradictory accounts of these 

 pests. The reason for this apparent contradiction is that under 

 these names are mustered quite a number of plants, all of which, 

 however, are members of the Grass family. The true Couch, 

 for which this particular name ought to be reserved, is Triticum 

 repens; the long underground stems of this plant, bearing scale 

 leaves and aerial branches, are so characteristic that they can 

 hardly be mistaken. At least five other grasses are covered by 

 the same name ; in fact, it appears that any grass receives this 

 general name which either runs along the surface of the soil 

 just above or just below it or which spreads out much and covers 

 any extent of ground with its branches. In Bedfordshire alone, 

 besides Triticum repens, the White Bent-grass {Agrostis stolo- 

 niferci), Field Foxtail or Black Bent {Alopecurus agrestis), Peren- 

 nial Rye-grass (Lolium perenne), Catstail or Timothy {Phleum 



' N. Passerini, Abst. in Exp. Station Records, U.S.A. xxiv. p. 30. 



