154 



Garden and Forest. 



[Number 425. 



and giving a unique aspect to the vegetation of our mountain 

 summits. 



All the activity and energy of the plant is brought to bear on 

 the development of the flower with its reproductive organs. 

 It is easy to understand, considering the conditions under 

 which they thrive, that alpine plants should require sometimes 

 several years to accomplish the cycle of their existence and 

 that they need more than a single season in which to produce 

 flowers and seeds. I have devoted much time and care to the 

 study and observation of the gradual growth of alpine plants, 

 and I am sure that certain large tufts of Androsace Helvetica 

 and A. pubescens, for example, have had more than a hun- 

 dred years of life. It is not hard to realize that the difference 

 of climate should materially alter vegetable forms. Our 

 humid, relatively short and warm winters, with the slow inter- 

 mediary spring season, followed by a hot dry summer, admits 

 of the gradual development of stems and leaves, and forms a 

 violent contrast to the climate of higher regions. There the 

 winter lasts nine months, or often more (as in certain narrow 

 valleys which are filled with snow frequently for years at a 

 stretch), and is followed suddenly by a short summer that is in 

 every way entirely favorable to rapid vegetable growth. As 

 soon as the snow melts, owing to the influence of the foehu, 

 the sirocco or other warm currents of air usually prevalent in 

 the mountains, the tawny color of the old decaying vegetation 

 changes rapidly in a few days, sometimes in a few hours, to a 

 brilliant green. As if by enchantment, the fields and rocks 

 become animated, are clothed with verdure, and everywhere 

 the beneficent fertilizing insects busy themselves over flowers 

 which, without their triendly interference, would remain 

 sterile. Some plants are so impatient to unfold their blos- 

 soms that they cannot wait for the melting of the surround- 

 ing snow, but push their flowers up through it, piercing it 

 easily, thanks to the dark color of their stems. This is often 

 observed on alpine pastures in the cases of Soldanella and of 

 the Crocus. But one questions how can that be if the plant 

 has remained dormant for eight or nine months. To which 

 the answer is, that the plant has been far from inert during the 

 winter, because, if it were so, it could not survive. Life and 

 action continue, sap and juices move, but slowly, and the 

 plant undergoes a gradual growth, the proof of which is as 

 follows : On the eastern slope of the Jura I have studied a tuft 

 of Soldanella for some successive seasons. My first observa- 

 tion was made during the last of October, as the winter was 

 about to set in, and the next day snow was falling rapidly, pre- 

 paratory to covering the ground for six long months. The 

 little plant had reached maturity, its sap was retreating into the 

 roots and it seemed about to die. At the first note of spring- 

 time I returned to the locality and carefully brushed the snow 

 from the spot noted the preceding fall, and found the plant 

 alive, showing flower-buds, though still very small, in the 

 centre of the little tuft. It had developed its buds in the same 

 way that the trees on the plains do theirs even during the most 

 rigorous of winters. The life of the plant is not reduced to as 

 dormant a state as is generally supposed to be the case, which 

 the breaking through of the snow by the early flowers of the 

 Soldanella and the Crocus readily goes to prove. As is well 

 known, the activity of the roots (and those of alpine plants are 

 very numerous) is concentrated almost exclusively on the re- 

 productive organs. The development of the foliage, which 

 contains the organs of respiration, is generally remitted to the 

 latter part of the summer, during and after the maturity of the 

 seeds. After the long winter's rest the plant enters into a pro- 

 digious and astonishing activity. The summer days are of 

 fourteen or even of sixteen hours of consecutive duration of 

 intense pure light ; the sun is hotter there than at lower levels 

 and water is plentiful, whether in liquid form or in that of 

 vapor. An abundance of light, an adequate amount of hu- 

 midity and a profusion of roots and rootlets are the sources of 

 life that keep these little plants in action. 



Let us now examine the conditions that cause the dwarfing 

 of alpine plants. In the first place, physiological experiments 

 have proved that it is during the night that tiie lengthening of 

 tissues and the gradual expansion of the plant occurs. In the 

 daytime, the greater the insolation, the less growth they ac- 

 complish, and the alpine night being so extremely cold, there 

 can scarcely be a question of nocturnal development of moun- 

 tain plants. It is under the influence of attenuated solar rays 

 and during the warm dusks that the plants are able to increase. 

 The powerful, exceedingly hot sun of high altitudes causes the 

 brilliancy and size of the corollas, but also prevents the equal 

 expansion of stems and leaves. These latter have only the 

 very short space of time between the setting of the sun and 

 the beginning of the glacial night for their growth, and conse- 

 quently they also profit by the short, cloudy, moist and tepid 



days that precede the setting in of winter to put forth new 

 leaves and buds. This is the general rule, though there are 

 scattered exceptions to it. 



The flora of polar countries has a very different aspect from 

 that of our mountains, though it has many species common 

 to both. There the sunlight is less intense, as well as more 

 constant, lasting as it does tor half of the year, but it is also 

 more diffuse, the solar rays being forced to pierce a much 

 thicker atmospheric stratum, and consequently the stems of 

 plants are more highly developed, floral colors are paler, the 

 foliage is less rigid and thick, and the blossoms are smaller. 



I have preserved in my herbarium some specimens of plants 

 common to both arctic and alpine regions, and the same spe- 

 cies show a very different form as found growing in the Swiss 

 mountains and in the boreal zone. Silene acaulis with us is 

 truly stemless and the flowers are sessile, while in Lapland the 

 name no longer applies, as there the much smaller flowers are 

 borne on peduncles measuring as much as ten centimetres. 

 There are also other causes that go to explain compression of 

 form in the vegetation of higher altitudes. Extreme violence 

 of storms and winds would destroy anything that did not cling 

 close to the soil, and icy nights force the plants to seek shelter 

 from the earth, which retains more heat than the air. Later 

 the extreme dryness of the atmosphere again obliges them to 

 look for protection from the ground, as the heavy dews that 

 provide the necessary amount of humidity required tor their 

 existence are preserved in its light and porous soil. This 

 same mountain soil is entirely different from that of the level 

 country, and is light, very porous and composed of decayed 

 vegetation and the pulverized rock common on the mountain. 

 That rock, whether calcareous or granitic, gives a chemical 

 character to the earth that greatly influences the plants which 

 thrive on it. There is a flora of granitic regions, another of cal- 

 careous or siliceous regions, and that especially so on high 

 mountains, as the alluvial soil of the plains is too great a mix- 

 ture for any appreciable influence to be felt. 



Director of the Alpine Garden at Geneva. H. Cor revolt. 



Foreign Correspondence. 



London Letter. 



Calpurnia aurea. — This is the Natal Laburnum of resi- 

 dents in south Africa, with whom it takes the place of the 

 common Laburnum of gardens in more temperate regions. 

 It has been in cultivation in a sunny greenhouse at Kew 

 for the last ten years, and is now a small tree about nine 

 feet high, with the habit, foliage and flowers of the com- 

 mon Laburnum, the main difference being in the smaller 

 flowers of the Natal plant. For countries where the tem- 

 perature is too high for the common Laburnum the Cal- 

 purnia would be valuable. It grows freely from cuttings. 



Cytisus proliferus is a shrub indigenous to the Canary 

 Islands, of which seeds were distributed from Kew in 1879 

 to Australia, India, etc., on account of its leafy branches 

 being useful as fodder. "Its great value is manifest from 

 the fact that it requires no irrigation, that it can grow in 

 comparatively barren land and that its branches can be cut 

 off three times during the year, resisting perfectly well a 

 long dry summer." Sheep are said to be very fond of it 

 and to thrive well when fed upon it ; it is also reported to 

 be good for ami relished by cattle and horses. In Australia 

 it is said to feed animals into condition more rapidly and 

 in a greater degree than any other food except corn, and it 

 grows rapidly in any kind of soil, growing to a height of 

 twelve feet or more in four years from seed. It flowers 

 freely from May to September and is a favorite with bees. 

 Dr. Schomburgk wrote in 1891 that he "considered it to be 

 one of the most valuable trees ever introduced into Aus- 

 tralia." Plants of it are grown at Kew for the decoration of 

 the conservatory. Here it forms a copiously branched 

 elegant shrub six feet high, not unlike the common C. 

 racemosus, except that the branches are longer and stiffer 

 and they are clothed in spring with paper-white flowers. 



Camellias as hardy shrubs are receiving attention in the 

 south of England, where they are proving as hardy as the 

 common Laurel and as floriferous as the Pontic Rhododen- 

 dron, so that the leading nurserymen in Devon and Corn- 

 wall are working up large stocks of them. At Kew they 

 are hardy, and this year they are flowering well. C. re- 



