Ailantus 



( 25 



Ajuga 



Other Species : 



Less elegant tliau the former are canina, nigra, 

 nibra and vulgaris. 



AILANTUS. 



(Ord. Simarubea'.) A splendid hardy deciduous 

 tree, but one that needs some shelter from cold 

 winds if its beauty is to be preserved. Its popular 

 name is Tree of Heaven. If young plants are 

 annually cut back close to the ground, and in the 

 following spring have the growths reduced to one 

 only, magnificent leaves are produced, which have 

 quite a tropical effect. Rich soil is necessary 

 under the latter conditions. 



Principal Species : 



glundulosa, 25'. Sep. 



AINSLI/EA. 



The only species in cultivation is a small-grow- 

 ing, rather woody plant (ord. Composita)), bearing 

 its Hower heads in racemes. Cool greenhouse treat- 

 ment, and a compost of loam, leaf mould, and sand, 

 will meet its requirements. After several trials the 

 plant cannot be recommended horticulturally. 



Species : 



Walkerrc, 2', Jan., bluish \vh. 



AIR. 



Our atmosphere is composed, broadly speaking, 

 of about four parts of nitrogen to one of oxygen ; 

 this also holds moisture in suspension, and it is 

 estimated that water is never represented by less 

 than one part in every hundred parts of air. In 

 addition to these, air contains about a tenth part of 

 1 per cent, of carbonic acid. Considering how 

 largely all these elements enter into the composi- 

 tion of plants, and to what extent they are ab- 

 sorbed through either leaf, stem, or root, it becomes 

 evident that plants cultivated under glass must 

 have regular supplies of fresh air. "Giving air" 

 and "airing" are technical terms generally under- 

 stood by horticulturists, but too often are only 

 considered as means of reducing the temperature. 

 With modern methods of building and heating it 

 should be easy enough nowadays to so ventilate 

 houses that while the occupants receive all the 

 advantages of fresh air, they are not subjected to 

 cold draughts and resulting attacks of mildew. 



Air in the form of gentle, flowing ' showers " 

 not strong, keen, concentrated "draughts'' is a 

 sovereign panacea for many ills to which plants 

 are heir. The amateur who sees his seedling 

 Stocks collapse is often awed when he learns that 

 there is a fungus with a formidable name at work, 

 but the trouble is just the familiar " damping-off," 

 which fresh air and judicious watering will prevent. 



The Grape grower who sees patches on his berries, 

 and knows that the dreaded " scald " has come, may 

 be inclined to bemoan the perversities of nature, 

 yet if he had got up early and given air before the 

 rapidly rising temperature had dried up the moisture 

 condensed on the surface of the berries, no scalding 

 would have appeared. 



At the time that this dictionary passes into the 

 press, horticulturists have before them the startling 

 pronouncement of Sir William Crookes relative to 

 the discovery of a means by which nitrogen can be 

 extracted from the atmosphere and applied to the 

 nourishment of crops. The Editor trusts to be 

 able to record successful experiments and the 

 establishment of the process on a sound commer- 

 cial basis in his Second Edition. 



AIRA. 



Graceful Grasses (ord. Graminea 1 ) easily grown in 

 fairly moist garden soil. 



Principal Species : 



caryophyllea, Jy., silvery. praecox, 2' to 3', My. , grn. 

 tlexuosa, !!'. (see alsoDeschampsia). 



pulchella, G" to 8". 



AITONIA. 



There is only one species of this genus (ord. 

 Sapindaeese),a shrubby evergreen requiring the tem- 

 perature of an ordinary greenhouse. Propagation 



STRIKING CUTTINGS UNDER A BELL-GLASS. 



is by cuttings of the young growths in very sandy 

 soil, under a bell-glass. Compost, peat and loam in 

 equal parts, with coarse sand. 



Species : 



capensis, 2', Jy., pk. 



AIZOON. 



South African succulent plants (ord. Ficoideae) 

 of no horticultural value. They require the tem- 

 perature of a greenhouse, with full sun and very 

 sandy soil. Propagation by cuttings and seeds. 



Principal Species : 



sarmentosum, 9", Jy., greenish wh. 



Other Species : 

 canarienae (wv Sesuvium lauceolatum, 1', Jy., red. 



Portulacastrum). perfoliatum (see Tetra- 



glinoides, 1', Jy., yel. gonia Zeyheri) . 



hisponicum, 9' , Jy., wh. 



AJUGA. 



A genus of about thirty perennials and annuals 

 (ord. Labiat(c). Propagated by division in spring 

 or autumn, or by seeds sown in the open in spring. 

 Common garden soil. The cultivated species are 

 hardy, and need no special attention, except to 

 prevent them from overrunning other plants. 

 Several of the species send out runners. 



Principal Species : 



genevensis, 1', My., etc., type bl., but varying to 

 pk. and wh. A pretty rock garden or border plant. 

 The best form is Brockbankii (syns. alpina and 

 rugosa). 



reptans, G", My., etc., bl. A useful carpeting 

 plant, thriving well in shade. The pur. leaved 

 and variegated forms are the best for the garden. 

 Grandiflora is good. 



Air pipes (see Heating). 

 Air Plant (see Aerides). 



