October 1, 1892.] 



KNOWI^EDGE. 



185 



the air for the blast, but furnishes power sufficient to drive 

 the blast engine. The arrangements for utQizLng the 

 formerly " waste " gases of the blast furnace have effected 

 a saving of more than half the total heating power of the 

 coke, a saving equal, in Great Britain alone, to about four 

 million tons of coal per annum. 



GRASSES. 



By J. Pextland Smith, M.A., B.Sc, Lecturer on Botany 

 at the Horticidtnral Colhye, Stranley. 



THE exceedingly natural group of plants known as 

 grasses constitutes a large part of the flora of the 

 British Isles, and is found generally diffused over 

 the surface of the globe, " from the utmost limits 

 of phrenogamous vegetation towards the poles, or 

 on alpine summits to the burning plains of equatorial 

 Africa." Some species arrest the traveller's attention' by 

 the'r wealth of numbers, some by the commanding height 

 which they attain, and others by both features combined. 



They may li%"e for one, two, or many years ; some spread 

 by means of underground stems, which send out roots 

 here and there to fasten the plant in the soil and obtain 

 fresh supplies of nourishment. In this way, certain 



species become troublesome 

 weeds, as the well-known couch 

 grass (Aiiiipyrum rcpenx). The 

 roots vary much in size ; in this 

 country, fi'om compact tufts, as 

 in the vernal grass [Anthox- 

 anthuni), to the enormously de- 

 veloped vertically descending 

 shoots of the wheat, which find 

 their way many feet down into 

 the soil. The root of the em- 

 bryo soon ceases to grow, and 

 numerous roots are developed 

 further itp on the stem to take 

 its place. These adventitious 

 roots are characteristic of mono- 

 cotyledons, or plants with one 

 seed leaf, to which the Gramineae 

 belong, although they are not 

 confined to this class. In Fig. 

 I., r, these adventitious roots are 

 seen ; the primary root is also 

 here, but even in tins early stage 

 is barely to be distinguished 

 from its adventitiousneighbours. 

 Each fibril is furnished with a 

 distance behind is clothed with 



Fig. I. — Germinating Oat. 



1. Showiug palese which re- 

 main attached to fruit ; i.p., 

 inner palea; o.^jjOuterpalea; 

 <•., earvopsis ; r., adventitious 

 rootlets ; a. .r ..portion of axis 

 of spikelet; ■«/., stem. 



2. Ihid, with paleae stripped 

 off. The origir^ of the root- 

 lets is clearly seen, eo., coleo- 

 rhiza ; v^, stem. 



3. Other side of 2, showing 

 origin of stem ; st., stem. 



root cap, and at some 

 absorbent root-hairs. 



At the points where the subterranean runners, or stolons, 

 send off" roots atrial stems also arise. These places are 

 called nodes, and the portions between internodes. Nodes 

 and internodes alternate in the same manner in the aerial 

 stem from whose nodes leaves only are normally developed. 

 Excepting at the nodes the aerial stems are hollow, and 

 there they are characteristicahy jointed. The nodal septa, 

 or divisions, are formed by the growing together of the 

 vascular bundles which, as continuation of the veins of the 

 leaves, run down the stem parallel to one another and to the 

 periphery. The sedges (natural order Cyperacese) are 

 nearly related to the grasses, and some of them are very 

 similar in appearance to their allies. The tubular stem of 

 the grasses and the solid stem of the sedges is, however, 

 a point of distinction easily noted. It is true that in hot 

 regions a few grasses, like the sugar-cane (Swrh.inim), have 



solid stems, and that the stolons of our British grasses are 

 not fistular, but a hoUow aerial stem is characteristic of 

 aU British species. 



Grass stems are always very slender. A remarkable 

 instance of this is found in the bamboo, which may grow 

 to a height of fifty feet, although the stem is only five 

 inches in diameter. The holljw nature of the structure 

 and the development of its strengthening tissue towards the 

 circumference render it able to resist effectively the strains 

 to which it is subjected. The result of the non-development 

 of the normal strengthening tissue, or sclerenehyma 

 {(TKXripi)^, hard, and ivyjiiLo., a tube), is sometimes seen in a 

 field of closely sown wheat, especially if the crop be a heavy 

 one and the season wet. The lower portion of the stem is 

 so shaded that assimilation is almost quite prevented, and 

 in consequence that portion is deficient in sclerenehyma, 

 resulting in the " laying " of the wheat. A large amount 

 of silica is present in some grasses, and this was considered 

 to be the strengthening material. " The thoughtless 

 assumption that the rigidity of the haulms of cereals is 

 essentially promoted by the sUica which they contain 

 impelled agriculcimsts, thirty years ago, to manure their 

 wheat fields with 

 costly preparations of 

 silica, hoping thereby 

 to prevent the lay- 

 ing of the wheat."* 

 Large deposits of 

 silica occupy the in- 

 ternodes of the bam- 

 boo. This substance, 

 known as tabascheer 

 or tabaxir, possesses 

 pecuUar optical pro- 

 perties. 



The leaves are 

 arranged on the stem 

 in two rows. They 

 have no petiole or 

 leaf-stalk, but the leaf- 

 sheath, which is split 

 down one side, is well 

 developed, and com- 

 pletely embraces the 

 stem. Where it joins 

 the blade or lamina, 

 there is a tongue or 

 ligule, generally of a 

 scarious nature. The 

 veins of the leaves, 

 as in monocotyledons 

 generally, run parallel 

 to one another. 



The flowers are 

 arranged indefinitely 

 on their axis, the older 

 flowers being below, 

 the younger above. 

 One flower, or two or 

 more arranged closely 

 together on one stem, 

 form a spikelet or 

 Uttle spike, + and „ ^ -n • , t j- 



,, 11 1 iio. V. — ramvie of A.iri ctespiosn. 



there are all grada- ' 



tions from a spike of one-flowered spikelets, as in the Timothy 



* Sichs, Phi/sioloifi/ of Plants, page 289. 



t A spike is an indefinite or racemose form of inflorescence, in 

 wliich the main axis is elongated and the individual floTvors sessile. 

 A raceme only differs from it in having stalked flowers. 



