52 



SCIENTIFIC NEWS. 



[July 20, 1 J 



cooled. The air then passes over the first steam coil, 

 and is heated sufficiently for the upper drying room. 

 After this it is again heated by the second steam coil, and 

 is used for drying in the lower room. Finally it serves 

 to remove the steam in the washing room. The whole 

 contrivance is at once simple and effective, and is a great 

 relief to the employees, who would otherwise have to do 

 their work under the usual very unhealthy conditions. 



■ — »-^»^^5«f-» — 



BUDS. 



{Concluded from page 34.) 



T T has been mentioned that lateral (not apical) buds arise 

 in the axils of the leaves, which is known as axillary 

 growth, and this mode of origin is characteristic of the buds 

 of all flowering plants except the gymnosperms, or plant 

 with naked seeds,such as the pines, which certainly produce 

 their lateral buds in the axils of their leaves, but not in the 

 axils of every leaf, as is usually the case with the other 

 flowering plants. In the cryptogams, or so-called 

 flowerless plants, lateral buds arise mostly near or 

 below the leaf. But even in the flowering plants various 

 deviations from the axillary mode occur, e.g., two or 

 three buds may be formed one above another {Loniccra), 

 or the bud may advance along the stem so as to be 

 above the axil, or the leaf may be formed late and ad- 

 vance upon the young shoot itself, appearing as its first 

 leaf. In flower-buds also — to which many of the details 

 concerning leaf-buds apply, flowers being composed of 

 modified leaves — the subtending leaf or bract is frequently 

 wanting. Still the bystem of axillary growth is pretty 

 constant, and Warming looks upon the leaf and bud in 

 flowering plants as a double organ, they being united at 

 the base. 



But this constancy of formation as buds is far from 

 being accompanied by constancy of development into 

 shoots, as many buds from want of sufficient nourish- 

 ment do not sprout at all; some, indeed, being suppressed 

 in a regular manner, giving a characteristic branching 

 to the plant. This latter feature is well shown in certain 

 members of the pink family (Caryophyllaceag) where the 

 leaves grow in pairs that cross each other, and only 

 one axillary bud is developed, giving rise to a spiral 

 arrangement. In certain plants (elm, hazel, and lilac) 

 the bud at the end of each shoot is suppressed, the next 

 below, which is lateral, continuing the growth. Termi- 

 nal suppression tends to produce bushiness, whilst 

 lateral suppression produces loftiness. The difference 

 of form thus brought about may be well contrasted in 

 the Lombardy poplar and the black poplar, the former 

 being tall and slender through the suppression of its 

 lateral buds, the latter short and spreading through the 

 suppression of its terminal buds. The greatest sup- 

 pression takes place in the Monocotyledons (plants with 

 generally parallel-veined leaves), and is well seen in 

 most palms, which produce their foliage-leaves in a 

 cluster at the top of an unbranched stem. It frequently 

 happens in plants, the buds of which are not sup- 

 pressed upon a regular plan, but from want of nourish- 

 ment, that these " dormant eyes " will sprout, an occur- 

 rence which generally takes place in consequence of the 

 access of more light and air, or more often through some 

 of the branches having been lopped off, as in pollards, 

 leaving an excess of nourishment in the plant that stimu- 

 lates the dormant organ to activity. 



These "dormant eyes" must not be confounded with j 



what are termined adventitious buds, the term adventi- 

 tious being used in opposition to normal, which, when 

 applied to buds, signifies that they are formed, as most 

 buds are, acropetally, or from the base to the apex of the 

 axis, no normal bud arising lower than one already exist- 

 ing, whilst buds are adventitious when they do so arise. 

 They occur in many ways, and seem to be the result of 

 an attempt on the part of the plant to get rid of exces- 

 sive nourishment and vitality. On old cut stumps they 

 appear upon the " callus," or cambium layer swollen 

 up between the bark and the wood, and upon detached 

 leaves and pieces of stem and root, especially when these 

 are kept in darkness. But it is chiefly on the leaves that 

 they are formed, as in the bulbils found in the angles of 

 the branching of the veins of the cuckoo flower {Car- 

 damine pralensis), and in the common water-cress 

 {Nasturtium officinale), and most strikingly in the centre 

 of the leaf of Nymphcea micrantha and in several of the 

 Aroidese, e.g., Athentrus ternaius, as tubers or bulbs 

 which separate and become independent plants. They 

 are found on the foliage-leaves of many monocotyledons 

 too, but remain in the bud condition so long as the mother- 

 leaf continues vigorous. They are very common on the 

 fronds of ferns (fig. 8) {Ceratopteris tlmlictroides, Asplcnium 

 caudatum, Woodwardia radicans, etc.), where, as in the 

 cuckoo-flower, they become vigorous, many-branched 

 shoots, which ultimately carry on an active individual 

 growth free from the parent. The male fern {Aspidium 

 filix-mas) produces no other lateral branches than those 

 which proceed from adventitious buds situated on the 

 basal parts of the backs of the older foliage-leaves. Not 

 infrequently the roots of plants give origin to buds which 

 develop into independent plants, the ordinary Acacia 

 being a familiar example, whilst on certain of the roots 

 given off, by the underground stem of the Bird's Nest 

 Orchis {Ncottia nidus-avis), a very rare mode occurs in 

 which the root-cap is torn off and the growing-point of 

 the root becomes a shoot. The origin of adventitious 

 buds has been usually considered to be what is termed 

 endogenous, that is to say, they arise from the internal 

 layers of the tissue of the axis producing them, which on 

 stems would be from under the bark or from its inner 

 layers, whereas normal buds arise exogenously, or from 

 the outer layers of the bark. But recent researches have 

 thrown some doubt upon the theory of the endogenous 

 origin of adventitious buds which Hoffmeister taught. Par- 

 ticularly pertinent are the experiments of Hanstein on the 

 cuckoo-flower and the water-cress,in which he shows that in 

 the epidermis, and subjacent tissue of fully-developed 

 leaves, certain changes occur, which transform permanent 

 tissue into embryonic, by which a conical growing-point 

 is produced, from which arise roots and leaves. With 

 regard to the adventitious buds formed on cut stumps, 

 these must be endogenous, as they spring from the cam- 

 bium layer, which is situated in the middle of the fibro- 

 vasular tissue of a plant. Indeed, until very lately, it 

 was thought that the normal buds of horsetails {Equise- 

 tums) were an exception, and arose endogenously ; but 

 it has been found that at the growing point their origin 

 is exogenous, and they become enveloped by the tissue 

 of the mother-shoot by subsequent changes. (Fig. 9.) Han- 

 sen has further shown that in Gleditschia the embryonic 

 tissue near the axil persists for a long time becoming 

 overgrown by the cortex of the current year's growth, 

 and that upon sprouting in the following spring the bud 

 appears to break through it, it being one of the ways in 

 which growing points are protected for future growth. 



