FRUITS REPLACED BY OFFSHOOTS. 463 



densis, 8. vulgaris, Ajuga Chamcepitys, Herniaria glabra, Viola tricolor, Cardamine 

 hirsuta, Medicago lupulina), normally annual, are transformed into perennial plants 

 when grown in my alpine experimental garden on the Blaser in Tyrol (Gschnitzthal), 

 at a height of 2200 metres, there being insufficient warmth there for them to produce 

 good seed. 



Interference with fruit-production due, in inhospitable situations, to an un- 

 favourable climate, can be artificially brought about by the removal of the flowers 

 from a plant as they appear. Annual plants pruned in this way produce shoots 

 and offshoots which would otherwise have remained undeveloped. These remain 

 living till next year, and if the same treatment be continued indefinitely, a plant, 

 otherwise annual or biennial, becomes perennial. Upon this fact depends the 

 gardening feat of producing little Mignonette trees. Normally the seeds of this 

 plant germinate in a sandy and humous soil, and the plants arising perish in the 

 autumn after flowering and ripening their fruit; but if the inflorescences be care- 

 fully pinched off, the stem doesn't die down but produces lateral shoots with the 

 object of developing new flowers. If these flowers be removed year after year, 

 gradually a little tree is formed, with woody stem and branches; and if ultimately 

 it be left alone will cover itself with hundreds of sweet-scented flower-spikes. 

 That a much increased production of leafy shoots and offshoots can be stimulated 

 in perennial plants by this kind of pruning has long been known; by its aid many 

 modes of propagation, as practised in horticulture and agriculture upon cultivated 

 plants, are obtained. 



It sometimes happens in nature that a failure of flowers is due to the plants 

 being overshaded. That is to say, many plants growing in shady places either 

 do not produce flowers or their flower-buds do not open and cannot ripen fruit. 

 Such plants produce offshoots from the lower portion of their stem in the form 

 of leafy shoots, runners, &c., if they are able to do so, and this in a very marked 

 degree; in other words, the more flowering and fruit-production is hindered by 

 shading, the more is a development of offshoots promoted. The Willow-herb 

 {Epilobium angustifolium) develops its beautiful flowers only in sunny situations, 

 accessible to hive- and humble-bees. The more intense the sunlight, the more 

 vividly are the flowers coloured. Should trees grow up and densely overshadow 

 the Willow-herbs, the flower-buds atrophy before opening and fall away from the 

 axis as small withered structures. Whilst the richly-flowering plants form only 

 short offshoots, these shaded plants produce long, subterranean runners, which seek 

 to penetrate to a distance, out of the circle of shade. 



Another remarkable phenomenon in the growth of perennial plants, which 

 flower and fruit copiously under favourable climatic conditions, is that in inhos- 

 pitable situations, where this is restricted, they propagate themselves very 

 readily by means of offshoots. A Composite, Nardosmia frigida, allied to the 

 Butter-bur, is widely distributed over the Arctic regions. Only towards its 

 southern limits does it produce flower and fruit; further north flowers are never 

 met with upon it, but, instead, it propagates itself far and wide by means of 



