INJURIES INDUCED BY PLANTS 



59 



d 



tributed in the seed-beds of conifers, where it may be met with 

 on the seedlings of every species. 



The disease may attack seedling beeches before they have 

 reached the surface of the ground, in which case a dark 

 discoloration spreads from the primary rootlet, and the plants 

 die off. Or, not till the 

 cotyledons have unfolded 

 does the stem above and be- 

 low them, or at their base, 

 become dark green and change 

 colour (Fig. 14, a,b) ; or simi- 

 lar spots may be recognized on 

 the cotyledons (Fig. 14, c), or 

 on the primary leaves (Fig. 

 14, d). Should the weather 

 remain long wet, decomposi- 

 tion quickly spreads over the 

 whole plant, while during dry 

 weather the plants wither and 

 assume a reddish brown and 

 scorched appearance. Young 

 sycamores, ashes, and robinias 

 show similar pathological 

 symptoms, and, in particular, 

 very black streaks will fre- 

 quently be found running up 

 or down the stem from the 

 base of the cotyledons. Fre- 

 quently it is only the apex of 



FIG. 14. Diseased seedling beech. Stem 

 below the cotyledons dark green at a ; 

 cotyledons diseased at b and c; first 

 foliar leaves showing blotches as at d. 



the stem and the leaves that 



become black, in which case 



the plant recovers ; but if, on 



the other hand, the lower part 



of the stem is attacked, recovery is impossible. Where the seeds 



of conifers are sown in rows, it is not unusual for a large number 



of the plants to perish before they have appeared above the 



surface of the ground. The roots and stems usually decay, 



and the young plants die or wither without any mechanical 



injuries being observable. It is worthy of note that, owing 



