456 THE ECOLOGY OF PLANTS. 



Goosefoots, Mallow, White Dead-nettle, Black Solanum, Hedge 

 Mustard, Cow Parsnip, etc. 



Also make observations, at different times of year, on the vegetation 

 of rubbish-heaps, pastures, roadsides, railway-banks (note the 

 differences between cutting's and embankments with regard to the 

 conditions of life and the plants found), garden borders, lawns, 

 ballast-hills beside seaports, pit-heaps beside collieries, waste 

 ground near mills, etc. On rubbish-heaps and ballast-hills we often 

 find alien plants (brought from foreign countries) along with such 

 plants as Annual Dog's Mercury, Teasel, Docks, Ragwort, Knotgrass 

 (Polygonum aviculare), Henbane (2-4 ft., leaves lobed sticky and 

 clammy, firs, with 5-lobed corolla yellow with purple streaks). Teasel 

 and Henbane often grow in waste places by the sea, and several plants 

 are rarely found except on rubbish-heaps or on rich waste ground 

 beside houses or farm-buildings, e.g. Greater Celandine (Ghelidonium, 

 Poppy family), White Dead-nettle. 



The vegetation of a lawn is often very interesting. The lawn itself 

 " consists of various grasses (species of Poa, Alopecurus, Cynosurus, 

 Festuca, Phleum, etc. ), often mixed with White Clover, but it usually 

 has various weeds which are well adapted to resist the lawn-mower, 

 e.g. Daisy, Dandelion, Plantain, Hawkweeds, Thistles, Cat's-ear, 

 Autumn Hawkbit, which have "radical" leaves in a rosette growing 

 close to the soil and kept there by the contractile roots, also coarse 

 rampant Grasses, like Couch-grass which spreads by long underground 

 runners. A damp or ill-kept lawn has a covering of feathery Mosses 

 on the soil, and is often invaded by various weeds which can compete 

 with the Grasses, e.g. Buttercups and even Horsetails. 



QUESTIONS ON CHAPTER XVI. 



1. For what different purposes do you consider that a plant requires 

 to be supplied with water? How are some plants able to withstand 

 long -continued drought uninjured ? Give instances of such plants. 



2. How does the climate inside a greenhouse differ from that with- 

 out? Name plants whose natural habitats are in climates (a) drier, (b) 

 wetter, (c) hotter, (d) colder than that of an English garden. What 

 arrangements would you make if you had to try to grow these various 

 plants in England? 



3. The island of Singapore produces more than 2,000 native species 

 of flowering plants ; the Isle of Wight (about equal in area) some 800 ; 

 an equal area in the Egyptian Desert less than 200. To what causes 

 would you attribute these striking differences ? 



4. How far do characters of the soil, other than its chemical nature, 

 determine the flora growing upon it ? 



