198 



HINTS AND NOTES 



factors. The lying of snow upon alpine 

 heit(hts, which are also wind-swepl, poor in 

 soil, and subject to insolation, retards the 

 flowering of alpine plants. 



The effect of size upon flowering is shown 

 by the earliest months of flowering of some of 

 the plants here included. Thus Vernal Whit- 

 low Grass, an annual, blooms in March. Field 

 Mouse-ear, Horseshoe Vetch, and Field Speed- 

 well bloom in April. Bird's-foot, also prostrate 

 and perennial, blooms in May. The annual 

 Rue-leaved Saxifrage, a mural plant, also 

 found on thin calcareous soils, flowers early in 

 April, whilst its taller relative. Meadow Sa.\i- 

 frage, blooms in May, on colder clay soils. 

 Mouse-ear HawUweed, Mother of Thousands, 

 and Silver)' Hair Grass flower in May. 



June is the month when numerous flowers 

 first open, viz. Cheddar Pink, Sandwort Spur- 

 rey, Navelwort, Biting Stonecrop, Houseleek, 

 Silky Wind Grass, Flat-stalked Poa, Sand 

 Fescue. Not a few, however, defer their 

 flowering till July, e.g. Orpine, Golden Rod, 

 Wall Lettuce, Rampion, Pellitory-of-the-wall, 

 and these are largely plants that grow in 

 crevices or walls, where the soil is poor or 

 thin, and nutrition a slow process. 



The Duration of Rock and Wall Plants. — 

 The duration of plants that are found upon 

 rocks and walls is regulated by various causes. 

 The arctic-alpine vegetation is exposed to such 

 adverse conditions that it is normally peren- 

 nial. But a few annuals are found even 

 amongst this group of plants, or of those that 

 range as high, e.g. Vernal Whitlow Grass and 

 Rue-leaved Saxifrage. Sandwort Spurrey 

 may be either annual or biennial, and House- 

 leek is perennial or biennial. The Rampion 

 is also a biennial. Grasses are usually peren- 

 nial, but some are annual, e.g. Silky Wind 

 Grass, Silvery Hair Grass, Sand Fescue. 



The remainder of the plants here considered 

 are perennial. This corresponds largely with 

 an increased stature or size, or with a diurnal 

 habit or late flowering period. 



The Pollination of Rock and Wall Plants.— 

 Growing in exposed areas, the arctic-alpine 

 chomophytes and chasmophytes are not char- 

 acterized by large or conspicuous or brilliant 

 flowers. But in sheltered positions the alpine 

 flora of Switzerland at much greater altitudes, 

 as is well known, is characterized by the 

 wealth and beauty of the flowers. It is true 

 that in such sheltered habitats in Scotland, 

 upon a small .scale, the same thing is to be 

 noticed, but the hills are not blue with the 

 flowers of Gcufiivia acau/is (erroneously re- 

 corded for Britain), or yellow with alpine 

 Wood .Anemones, &c. Still, the arctic tvpes 

 of Pinks, Stitchworts, Saxifrages, Primulas, 



&c., reflect in a lesser degree the grandeur of 

 the alpine flower garden. 



As a whole the flowers of the plants here 

 enumerated are not large or conspicuous. The 

 bulk are cross-pollinated b\' insect agency, but, 

 as is inevitable with small-flowered f)lants, 

 many are equalh' adapted to self-pollination. 

 Some, indeed, such as Vernal Whitlow Grass 

 and Ivy-leaved Toad -flax are specially fitted 

 for the latter, the stigma and anthers ripening 

 together. In the case of Cheddar Pink, Rue- 

 leaved Saxifrage, and Orpine the anthers 

 mature before the stigma, and in the case of 

 Pellitory-of-the-wall, Sand Fescue, &c., the 

 stigma is developed and receptive before- 

 hand. 



Cleistogamy occurs in the case of Ivy-leaved 

 Toadflax. Pollination by the assistance of the 

 wind is exemplified by such Grasses as Silky 

 Wind Grass, Silvery Hair Grass, Flat-stalked 

 Poa, and Sand Fescue, and by the Pellitory-of- 

 the-wall. 



Dispersal of Fruits and Seeds of Rock and 

 Wall Plants. — Amongst the rock and wall 

 plants there are few if any plants, at least 

 amongst those enumerated here, that are 

 adapted to dispersal of fruit or seed by the 

 agency of animals. The absence of aquatic 

 conditions, also, is marked by the entire ab- 

 sence of water-dispersed fruits or seeds. 



In the exposed habitats in which a large 

 bulk of this class of plants grow, it is, more- 

 over, quite natural that the majority of plants 

 growing upon rocks and walls should be 

 adapted to dispersal by aid of the wind. 

 It must be remembered, however, that it is 

 necessary for plants, growing upon such 

 limited areas as the specially suitable rocks 

 or walls usually are, to be dispersed at no very 

 great distance from the plant. The following 

 are wholly or partly dispersed by the agency 

 of the wind, viz.: Wallflower, Cheddar Pink, 

 Field Mouse-ear, Bird's-foot, Horsevetch, Rue- 

 leaved Saxifrage, Meadow Saxifrage (censer 

 fruits), Navelwort, Orpine, Stonecrop, House- 

 leek (small seeds), Golden Rod, Mouse-ear 

 Hawkweed, Wall Lettuce (with hairy pappus), 

 Rampion (censer fruits), Field Speedwell, 

 Pellitory-of-the-wall, Silky Wind Grass, Silvery 

 Hair Grass, Flat-stalked Poa, Sand Fescue. 



The rest, e.g. Yellow Fumitory, Whitlow 

 Grass, Sandwort Spurrey, Ivy-leaved Toad- 

 flax (which buries its fruits in the crevices of 

 the wall), have mechanisms or methods of 

 dispersal of their own. 



The Soil of Rock and Wall Plants. — In the 

 case of pctrophvtes or plants that grow upon 

 rocks, or rock debris, or in crevices, the com- 

 position of the rock is of import.ance in deter- 

 miTiiiig distribution. But since the highest 



