THE NATURALISED PLANTS. 131 



Others flourish, it is true, but, lacking adaptability, are narrowly 

 restricted to a definite and well-defined station out of which they 

 cannot go. On the shores of Cook Strait the horned poppy (Glau- 

 cium ftavum) is confined to gravelly and stony beaches. On the 

 clavev hillside near Lvall Bay is a fine colony of this striking plant, 



J J !/ / V 



with its silvery foliage and delicate yellow flowers ; but it is strictly 

 limited to a spot where a quantity of gravel and coarse sand has col- 

 lected. The well-known marram-grass (Ammophila arenaria) can 

 grow only where there is drifting sand. Cut off the supply, and the 

 green leaves quickly assume a sickly yellow hue, and, if no more sand 

 comes, the plant will eventually die. Certain species may become 

 established in a few places, but can spread no farther. Especially 

 is this the case with the plants of old gardens, which may linger for 

 years, but, failing to reproduce their kind, finally die out. Lastly, 

 many species thrive well for a time, but are eventually eradicated 

 by more vigorous competitors. 



Nowhere can this last example be better seen than in pasture 

 land. At first the newly laid-down grass may consist of valuable 

 rye-grasses (Lolium perenne, L. italicum] and clovers. In time, owing 

 to its perennial habit, the first-named will overcome the annual species, 

 which is unable to reproduce itself freely from seed on the closely 

 occupied ground. The adult plant, too, dies at the end of the year. 

 Next, through the action of cattle, sheep, and horses, the perennial 

 rye-grass is eaten to the ground, while those grasses worthless for 

 feed which have crept in, such as the soft brome-grass (Bromus Jior- 

 deaceus) and Yorkshire fog (Holcus lanatus), increase at a great rate, 

 their flowers being untouched and their reproduction not hindered. 

 Finally, the pasture deteriorates so much that it must be broken up 

 and laid down afresh. 



Before leaving the question of weeds, those minute organisms 

 must be mentioned which, settling down upon other plants and 

 living as parasites, damage and not infrequently kill the host. To 

 this category belongs that vast assortment of non-flowering plants 

 commonly termed " blights." Many of these are members of the great 

 family of fungi. For the most part they are more or less invisible 

 without the aid of the microscope, but their presence is often writ 

 large on the unfortunate host-plant. The rusts and smuts, the so-called 

 Irish potato-disease, the organism causing "damping off" in seedlings, 

 and many and diverse causers of plant-diseases belong to the " blights." 



