508 DEPENDENCE OF PLANT FORM ON SOIL AND CLIMATE. 



killed by the isolated frosts which occurred in each of the six years of the experi- 

 ment, not only in the last week of June, but during July and August; but others 

 (e.g. Agrostemma Githago, Centaurea Cyanus, Iberis amara, Lepidium sativum, 

 Satureja hortensis, Senecio vulgaris, Turgenia latifolia, Veronica polita, Viola 

 arvensis) only underwent a short temporary stoppage of growth from this cause, 

 and opened their flowers at the end of August and beginning of September. In 

 the plants of some species (e.g. Senecio vulgaris, Veronica polita, Viola arvensis) 

 ripe seeds capable of germinating were formed in September. The flowering speci- 

 mens, in comparison with those which had grown during the short days of the 

 spring exposed to numerous night-frosts in the Vienna gardens, displayed extremely 

 shortened internodes. The number of internodes was also lessened, or rather, 

 fewer were developed. For example, where 10 internodes developed in an experi- 

 mental plant in Vienna, in the Alpine garden a corresponding plant would only 

 have 5-6. The same was true of the development of the flowers. While in a plant 

 of Viola arvensis in Vienna the axillary buds of the first six foliage-leaves were 

 suppressed and flowers were not produced until the seventh and eighth leaves, 

 flowers grew from the third and fourth axillary buds in the same species of plant 

 grown in the Alpine experimental garden. The number of flowers on a plant was 

 less, the petals were smaller on the average, and, generally speaking, the annual 

 plants in the Alpine garden had the same appearance as those grown in the plain 

 on dry, sandy soil described on p. 500. It has already been stated on p. 453 that 

 some of the species which are annuals in the valley and on the plain do not die 

 in the autumn in the Alpine garden, but remain alive through the winter and in 

 the following year develop new shoots from the stem. 



To describe the alterations undergone by biennial species in Alpine regions we 

 will take Libanotis montana (an Umbellifer) as an example. Its stem in the 

 Alpine garden was 16-24 cm. high and developed 5 internodes which were 2-5 cm. 

 long. From the axils of the 5 green stem-leaves sprang lateral shoots which did 

 not branch but terminated in a single umbel, so that the plant only bore 5 umbels 

 altogether. The plants grown from similar seeds in the Vienna Botanic Garden 

 exhibited a stem more than a metre high with 10 internodes each 10-20 cm. long. 

 No lateral shoots were produced from the axils of the lower stem-leaves. Those 

 from the axils of the middle and upper leaves were branched and bore several 

 umbels. On an average a plant had about 20 umbels altogether. 



Over 300 species of perennial plants were grown in the Alpine experimental 

 garden. Only 32 of them blossomed, however. Those whose flowers usually pre- 

 cede the foliage-leaves were in full blossom at the beginning of July, the others, 

 which had to develop a leafy stem before their flowers appeared at the top or 

 in the axils of the leaves of this stem, did not flower until the end of August and 

 beginning of September. Three species of the latter kind will be more particularly 

 treated of here; one species whose stem bears only a single leaf and is terminated 

 by a single flower (Parnassia palustris), one whose stem is beset with decussate 

 leaves and terminates in a loose inflorescence composed of small cymes (Lychnis 



