Chap. XVIII. CHANGED CONDITIONS. 147 



specified, there are many plants in which the reproductive system 

 has been seriously affected by the altered conditions of life to 

 -which they have been subjected. 



It would be tedious to enter on many details. Linnaeus long 

 ago observed 7S that Alpine plants, although naturally loaded with 

 seed, produce either few or none when cultivated in gardens. But 

 exceptions often occur : the Drdba sylvestris, one of our most 

 thoroughly Alpine plants, multiplies itself by seed in Mr. H. C. 

 Watson's garden, near London ; and Kerner, who has particularly 

 attended to the cultivation of Alpine plants, found that various 

 kinds, when cultivated, spontaneously sowed themselves. 79 Many 

 plants which naturally grow in peat-earth are entirely sterile in our 

 gardens. I have noticed the same fact with several liliaceous plants, 

 which nevertheless grew vigorously. 



Too much manure renders some kinds utterly sterile, as I have 

 myself observed. The tendency to sterility from this cause runs 

 in families ; thus, according to Gartner, 80 it is hardly possible to 

 give too much manure to most Gramineae, Cruciferae, and Legu- 

 minosae, whilst succulent and bulbous-rooted plants are easily 

 affected. Extreme poverty of soil is less apt to induce sterility ; 

 but dwarfed plants of Trifolium minus and repens, growing on a 

 lawn often mown and never manured, were found by me not to 

 produce any seed. The temperature of the soil, and the season at 

 which plants are watered, often have a marked effect on their 

 fertility, as was observed by Kolreuter in the case of Mirabilis. 81 

 Mr. Scott, in the Botanic Gardens of Edinburgh, observed that 

 Oncidium divaricatum would not set seed when grown in a basket 

 in which it throve, but was capable of fertilisation in a pot where 

 it was a little damper. Pelargonium fulgidum, for many years after 

 its introduction, seeded freely; it then became sterile; now it is 

 fertile 82 if kept in a dry stove during the winter. Other varieties 

 of pelargonium are sterile and others fertile without our being able 

 to assign any cause. Very slight changes in the position of a plant, 

 whether planted on a bank or at its base, sometimes make all the 

 difference in its producing seed. Temperature apparently has a 

 much more powerful influence on the fertility of plants than on 

 that of animals. Nevertheless it is wonderful what changes some 

 few plants will withstand with undiminished fertility : thus the 

 Zephyranthes Candida, a native of the moderately warm banks of the 

 Plata, sows itself in the hot dry country near Lima, and in Yorkshire 



78 'Swedish Acts,' vol. i., 1739, Chronicle,' 1848, pp. 253, 26S, and 

 p. 3. Pallas makes the same remark mentions a few which seed. 



in his 'Travels '(Eng. translat.), vol. i. so ' Beitr'age zur Kenntniss der 



p. 292. Befruchtung,' 1844, s. 333. 



79 A. Kerner, 'Die Cultur der Al- 81 'Nova Acta Petrop.,' 1793, p. 

 penpflanzen,' 1864, s. 139; Watson's 391. 



'Cybele Britannica,' vol. i. p. 131; 82 'Cottage Gardener,' 1856. pp 



Mr. D. Cameron, also, has written on 4 4, 109. 

 the culture of Alpine plants in ' Gard. 



