September 22, 1888.] 



THE GARDENER S' CHR ONI CL E. 



325 



The different forms of the acaulis group are con- 

 sidered to be species, and consequently the old 

 original type of aoaulis only exists in an historical 

 sense. These forms are maintained in the garden 

 here by propagation and by seeds. 



Gentiana alpina of the fields, &c, must be excluded 

 from these notes, as I have never been able to obtain 

 seeds of the true form. It is more rare than it is 

 generally thought to be, but I hope to discover it 

 this autumn and collect seeds. 



The species I have grown from seed are Gentiana 

 Clusii, G. angustifolia, and G. Kochiana. 



erect, of an azure-blue colour with five bright green 

 spots in the throat. It is the most beautiful species, 

 and also the most easy to cultivate. A sowing made 

 in 188G produced flowers last spring, whereas with 

 other species three or four years elapse before flower- 

 ing. G. angustifolia is a native of the limestone 

 mountains of the La Grande Chartreuse region be- 

 tween Chambery and Grenoble, and consequently re- 

 quires a limestone soil. 



G. Kochiana has large, very broad leaves, of a moss- 

 green colour, which spread out on the soil. It is the 

 most curious Gentian, and its foliage is the richest, 



T 



J 



l'"lG. 42. — CHIRONIA TEDUNCDLARIS: GREENHOUSE PLANT: FLOWERS PURrLE. (SEE P. 324.) 



G. Clusii is a relatively scarce species, a native of 

 the Jura chain and of the limestone Alps (altitude 

 1500—2000 metres = 5000 to 6000 feet). The 

 leaves are shining, thick, leathery, lanceolate, and 

 very pointed. The teeth of the calyx are separated 

 by an acute sinus (interspace). The flower is of a 

 beautiful deep blue colour, and has no green mark- 

 ings in the interior. This species lives and flowers 

 well in our garden here, but makes few runners, and 

 takes a long time to increase the size of the tuft. It 

 does not flower again in autumn. 



G, angustifolia is truly the most beautiful species of 

 the genus. It has oblong, sometimes very elongated 

 leaves, straight and narrowed towards the base. The 

 divisions of the calyx are abruptly acuminated and 

 contracted towards the base. The flower is large, 



but its violet-blue flowers are not so beautiful as 

 some others. There are five dark green spots in 

 the throat. It is essentially a native of the Valais, 

 and occurs in all pasturages between 2500 and 3000 

 metres elevation. It shuns lime, and belongs to 

 the granitic flora. It is acclimatised here, but does 

 not flower well. 



G. alpina is one of the prettiest and most interest- 

 ing species, but, unfortunately, it is rare and of diffi- 

 cult cultivation. The foliage is glaucous, and forms 

 an incurved imbricated rosette, whence springs one 

 little flower of an azure-blue colour. Its habitat is 

 at once that of G. acaulis and of G. verna. It pro- 

 duces runners freely. G. alpina is only found on 

 primitive rocks at an elevation of 2500— 3000 metres, 

 and is only to be seen on the Alps. 



A fifth form of G. acaulis has been found in the 

 mountains of Bosnia, and is described by Dr. Giinther 

 Ritter von Beck in the Flora of Bosnia (Abhandlung 

 des K. K. Natur. Hofmuseums in Wien). 



Of all these species it is very certain that G. angus- 

 tifolia is the best to cultivate, being the prettiest, 

 and the one most easily grown (excepting the 

 English Gentianella). It frequently flowers again 

 in the autumn, and is covered with its fine bell- 

 shaped flowers in the spring, and does not suffer from 

 our relatively dry atmosphere. H. Corrcvon, Jardin 

 Alpin d'Accliinatation a Geneve. 



THE CHEMISTRY OF VEGETA- 

 TION, IN REFERENCE TO THE 

 GROWTH OF THE POTATO. 



(Continued from p. 208.J 



Boussingault. — When once this kind of investiga- 

 tion was fairly "set going "a number of experimenters 

 in different countries took the subject up. By 

 the time Boussingault — who had studied chem- 

 istry at a mining school — was led, through his 

 marriage with a sister of M. le Bel, to take up 

 " agricultural chemistry,'' there was also a large 

 amount of information in the shape of papers com- 

 municated to learned societies and journals. On his 

 brother-in-law's estate at Bechelbronn (in Alsace) 

 he commenced a series of analyses of plant com- 

 position. One of his earliest inquiries was on the 

 amount of nitrogen present in forage plants, and on 

 the results he obtained he published a paper in 

 1836.* The following year he was appointed Pro- 

 fessor of Agricultural Chemistry at the Conservatoire 

 des Arts et Metiers, and took in hand the question, 

 whether plants obtain their nitrogen from the air? 

 On this he published, in 1838. t With the numerous 

 analyses made at this period by many chemists of 

 the composition of plants, and the chemical consti- 

 tution of vegetable acids, we are at present but little 

 concerned. 



Paten. 



It should be noticed, however, that in 1836 and 

 1837 Payen wrote papers on starch (amidon) in 

 the Annates de Chimie. et de Pliysique,\ and made 

 careful analyses of starch obtained from different 

 plants. Chemistry in its application to the Arts 

 and to manufactures and to pharmacy, went 6teadily 

 on, and the philosophic explanations of chemical 

 actions was the subject of frequent thought by 

 philosophic minds. It is, however, only in so far 

 as their " principles" bear on the present subject that 

 they need here be referred to. 



Alongside of the ever widening attention to 

 analyses and to the physics of chemistry a new branch 

 of research, which has proved of such fascinating 

 interest to many, was springing into existence. 



Here it is necessary to look back somewhat in 

 time from the date of Boussingault's paper just men- 

 tioned. 



Priestley had, as far back as 1779, written : — " I 

 have been so happy as by accident to have hit upon 

 a method of restoring air which has been injured 

 by the burning of candles, and to have discovered at 

 least one of the restoratives for this purpose — it is 

 vegetation." [A plate showing his simple method 

 of observation is given with his paper.] 



Ingenhousz, Senebier. 



But it was Ingenhousz, of Breda, then living in 

 London, who at the same time (1770) first clearly 

 defined the relation of the plant to the atmosphere, 

 and showed that the absorption of the carbonic acid 

 by the plant was dependent on the influence of the 

 light of the sun, and not of the heat. Senebier, of 

 Geneva, also in 1779 took the subject up, and in 1782 

 gave his first important paper. 



In 1792 he published in the Journal de Physique 

 his memoir " On the great probability that carbonic 

 acid gas is decomposed by plants in the process of vege- 

 tation." Continuing his researches, he in 1802 pub- 



» Ann. de Chit 

 t lb. , vol. Isvi 



e et Physique, vol. lxiii., p. 225. 

 , p. 5. I lb., vols. lxi. 



