A SECOND OHIO WEED MANUAL. 293 



Perhaps the first point, robbery of the soil moisture through weeds, 

 is one of the chief; this is especially true in fruiting orchards dur- 

 ing drouth, when any removal of moisture b}- other plants may 

 cause serious damage. I regard the robbery of moisture as a lead- 

 ing" form of injury. Crowding causes large injury, particularly to 

 young seedlings in cultivation. The third form of injury is general, 

 like the first and second, but probably has .been given its full value. 

 Soil robbery and crowding as well as many other forms of injury 

 will be in proportion to the number and growth of these persistent 

 invaders. Enlightened practice will appreciate the matter of 

 harboring injurious fungi by w T eeds, as for example, barberry and 

 wheat rust; the same applies to insect harbors. 



The simple cost of weed removal along the railways of the State 

 of Ohio is placed by Stair at over half a million dollars per annum. 



INTRODUCTION AND SPREAD OF WEEDS. 



We have seen that weeds arise from their adaptation to the con- 

 ditions man has brought about on the earth. The mutual plant and 

 soil characters count for much here. With the continuous changes 

 being wrought, new plants come into any given region. Some ot 

 them prove adapted to the conditions offered and show great powers 

 of growth and reproduction. The Russian thistle illustrates the 

 point fully. Bracted-plantain, broom-sedge, penny-cress, spreading 

 mustard and a host of others give the same evidence. Yet plants 

 may grow harmlessly for a long time in a given situation to become 

 aggressive in another. The tickseed sunflower, Bidcns trichospcr- 

 ma, is found in swarapj' places. In a part of Mahoning count}', as re- 

 ported by Mr. Vickers, it became transplanted to upland roadsides, 

 showing remarkable vigor in this new habitat. While a slight 

 change of location may result in a change of habit, by far the com- 

 moner source of new pests is by introduction from remoter regions. 

 There appeared in Ohio, to the writer's knowledge, in 1896, two 

 plants newly introduced from Europe, both of them new to the 

 United States as well as this state. They are a very small flowered 

 catchfly, Silcnc conica L., found in crimson clover at Clyde, Ohio, 

 and sandwort plantain, Plantago arenaiia L., in the city of Dayton, 

 iFig. 56). It is to be noted that this is the third of the introduced 

 species of plantain — narrow and bracted-plantain are quite well 

 known as weeds in Ohio. Half a century ago numerous species, now 

 weed pests, were unknown in the state. 



