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IRISH GARDENING. 



jLNIi 



This elons,-ated cell is hollow ;iiul tilled with 

 tluid (.cell sap), while its wall is Loniposed ot 

 \ei,'-etahle membrane. There is no openiiii,'- in 

 the cell, so that it is by no means apparent how 

 the water from the soil carryinj,'- the materials 

 for nutrition In solution ean enter the root. 

 However, it may be shown by a simple experi- 

 ment that, if a ve^'etable membrane separates 

 two liquids eontainini,'- substances In solution, 

 and one liquid Is more concentrated than the 

 other, then the weaker tluid will diffuse throuj^h 

 the meinhrane into the more concentrated one. 

 and this is what happens with the root hair and 

 the soil water. The cell sap of the root hair 

 is more concentrated than the soil w-ater, con 

 sequently the latter passes throui^h the cell 

 membrane into the root hair. Thence it 

 diffuses into the neii^-hbouring cells of the I'oot 

 until it reaches the vessels which stretch from 

 the central core of the root upwards to the 

 veins of the leaves like sets of water pipes. I'p 

 these the soil water Is forced, how exactly we 

 do not know, and finally the leaves are reached, 

 when part of the water Is evaporated off into 

 the air, part used In the manufacture of starch, 

 and the dissolved salts built Into complex food- 

 substances of value to the plant. 



But why, we mig-ht ask, does the root hair 

 cling- so tightly to the particles of soil If its 

 object is merely to obtain soil water? The 

 answer to this is that in all except water-logg^ed 

 soils or immediately after rain the water 

 surrounds the particles of soil in the form oi' 

 thin films and does not fill the interspaces 

 (which contain air), and It Is to draw upon these 

 encircling- films that the root hair cling-s so 

 tlg-htly to the particles. 



The absorption of water is not confined to 

 those cells of the root epidermis which are pro- 

 longed Into root hairs, but also takes place 

 through the ordinary flattened cells of the root 

 skin. Some conifers possess no root hairs, 

 while In the case of water plants they are very 

 seldom present, as these plants do not have to 

 seek for their water supply. 



Roots, In common with all other organs of 

 the plant, absorb oxygen from the air and give 

 off carbonic acid ; In other words, they breathe. 

 Hence the necessity for a well-aerated soil for 

 all except marsh or water plants, the roots of 

 which have adapted themselves to more or less 

 airless conditions. The sickly appearance of 

 an overwatered pot plant Is principally due to 



root sutlocation. Tiic carbonic acid gas ex- 

 cretetl l->y the voo\ becomes dissolved in the 

 soil water aiul acts as a weak acid in breaking 

 (.louii and rendering soluble some oi the 

 iniiK'ial constituents ol the soil, thus enabling 

 Ihein to bo absorlu-d iiy the roots. If seeds are 

 germinated in contact with a slab oi' smooth 

 marble the young roots, where they touch the 

 marble, may be seen to etch its surface owing 

 to the dissolving action ol' the carbonic acid 

 which they excrete. 



The roots of many forest trees are helped 

 by certain fungi which attach themselves to the 

 roots, and in return tor a certain amount ol 

 nourishment help to change the leaf-mould into 

 such a condition that it can be alisorbed by the 

 roots of the tree. A souKwlial similar arrange- 

 ment for nuiliial i-ienefit exists in the case of 

 the bacteria inhabiting the swellings on the 

 roots of leguminous plants which render the 

 nitrogen of the air available as plant food. 



In the case ol' semi-parasitical or wholly 

 parasitical plants the roots have partly or 

 entirely lost their functions, and the plant 

 attaches itself by suckers to the roots or 

 branches of other plants. The Eyebrlght, Yellow- 

 Rattle and Lousewort ol' our pastures are 

 examples of semi-parasitical degenerates, while 

 the mistletoe does not attempt to obtain any 

 food materials from the soil for Itself. The 

 aerial roots of orchids hanging from the 

 branches of the trees In a tropical forest are 

 enveloped in a parchment-like sheath which can 

 absorb moisture from the air and hold It like 

 blotting paper, thus they fulfil in the air the 

 absorptive functions which other plant roots 

 perform in the soil. 



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High upon the bleak clift' where the wild wind dashes 



Grows that little g:arden which my soul loves best, 

 Filled with flower-faces, white and blue and yellow, 



Sheltered from the east wind, but cradled by the west. 

 Tossed against its limestone clings one pallid Woodbine, 



Spreads the golden Trefoil, %vaves the Hairbell tall, 

 Saxifrage and Hedstraw, Pimpernel and Eyebright, 



One little hollow rift finds room enough for all. 



Close along its ledges cluster snowy Dryas 



Roses are the flowers, yet it clutches hard the rock. 

 Claw-like its rootlets, roots like claws of seagulls. 



Scornful of the tempest, and proof 'gainst every shock. 

 Campions fill the corners, careless little growers, 



Loved of the roving moth, which visits them at night ; 

 Under silvery leaflets round, balloon-like blossoms 



Tumble in a tangled mat, mingled green and white. 

 —Emily Lawless. 



