October 1, 1892.] 



KNOWLEDGE 



187 



sac being fiDed with nourishing matter called endosperm 

 ('evJo, within, and atrspij.a,, a seed). Only a small part of 



S 







■J^?-^>^^, 



J.*t*^ 





'■ P,. 



Fig. III. 



1. Spikelet of the Pereunial Rye Grass (Lolitnn 

 perenne) ; _/"., filament ; an., anthers ; i. p., inner palea ; 

 o.y>., outer palca ; .9^., stignia ; j., glume. 



2. Gvniecium of Lolhim perenne. 



the endosperm is sliowu in the figure, but enough is 

 portrayed to show tliat it is diiJ'erentiated into a yellowish 



and a whitish jjortion, 

 f^;* the former rich in ni- 



trogen (albuminoid), 

 the latter starchy. 

 The embryo is com- 

 posed of two main 

 portions, the radicle 

 and plumule. The 

 lower portion of the 

 radicle is the primary 

 root, and the upper 

 part the hypocotyl 

 ('i/TTo, under) or por- 

 tion below the cotyle- 

 don or seed leaf. The 

 ■plumule is the epi- 

 cotyledonary part covered by its young leaves. This will 

 afterwards form the greater part of the stem of the plant. 

 The growing apex of the plumule is seen at "/'. The embryo 

 lies outside the endosperm, but it is attached to it by a 

 large shield-shaped development of the hypocotyl, which 

 at ihe same time nearly encloses the embryo itself. 

 The epithelium of the scutellum, as this extraordinary 

 structure is called, secretes ferments which digest the 

 nourishing matter of the endosperm, changing the in- 

 soluble starch into soluble sugar, and the insoluble nitro- 

 genous matters into soluble forms. These chemical changes 

 commence when tlie mature fruit is placed in a moist 

 medium, supplied with oxygen, and kept at a proper 

 temperature. The soluble nutritive substances are trans- 

 ferred to the embryo plant by way of the scutellum, which 

 thus acts like a placenta, and the seed commences to 

 germinate. The radicle is pushed out of the fruit and the 

 pirimary root penetrates the soil. Then the plumule makes 

 its appearance, but the scutellum still remains attached to 

 the endosperm, so that the seedling is still parasitic on the 



Fic. IV.— .'^iiikolct of Yorkshire Fog 

 (Holriis lannliis); «.!■., stalk of spikelet; 

 ax'., axis of ilowers of spikelet ; g., glume ; 

 (/. p., outer pajea ; i. ji., inner palea ; a.. 

 awn of glume; «'., awn of outer palea of 

 upper llower; "«., anthers; c, gyncpcinm. 



seed. Gradually the endospei-m is used up, and by this 

 time the roots have penetrated the soil and chlorophyll 

 bearing leaves have so developed as to enable carbon 

 assimilation to proceed sufficient for the needs of the seed- 

 ling. The young plant can then elaborate food material 

 for itself. 



The delicate apex of the root is protected by a cap of cells 

 (»•.(•). The roots of grasses 

 are enclosed in a sheath 

 (r. s), which they break 

 through in germination, 

 and which then surroimds 

 their base like a coUar. It 

 is called ihevolvorliha I'/i-i^a, 

 a root). This structure oc- 

 curs in some other mono- 

 cotyledons and in a few 

 dicotyledons. Adventitious 

 roots are developed from 

 the hypocotyl, and rupture 

 the enclosing tissue, .which 

 remains like a collar, as in 

 the ease of tlie root-sheath. 

 The primary root of the 

 maize remains for a com- 

 paratively long period much 

 larger than the secondary 

 roots. In the oats, at a 

 very early period of germi- 

 nation, it is a matter of 

 some difficulty to deter- 

 mine the primary root (see 

 Fig. I.). But in any case 

 the primary root soon dies 

 away, and the development 

 of a large number of adven- 

 titious roots produces the 

 fibrous roots common to the majority of monocotyledonous 

 plants. 



The products derived from grasses are extremely various, 

 and the plants furnishing these are very numerous. The 

 most familiar examples of economical products are derived 

 from the cereals — wheat, barley and oats. The origin of 

 the two former is shrouded in mystery. They have both 

 been cultivated i)i prehistoric times, and consequently to 

 establish the home of the wild species in each case is a 

 matter of great difficulty. " Very ancient Egyptian monu- 

 ments, older than the mvasion of the Shepherds, and the 

 Hebrew scriptures show this (the wheat) cultivation 

 already established, and when the Egyptians or Greeks 

 speak of its origin they attribute it to mythical personages, 

 Isis, Ceres, Triptolemus." * De Candolle also states that 

 the Chinese, who cultivated wheat in b.c. 2700, considered 

 it a gift direct from heaven, and that it is one of the five 

 species of seeds annually sown in the ceremony of sowing 

 five kinds of seeds— rice {Unjzu), sorghum (a kind of 

 millet), Si'tarii) itdlini (another kind of millet I. and soy 

 being the others. He considers the Euphrates valley to 

 be the probable home of the species. The account given 

 by the same authority of the supposed mummy-wheat 

 is worth quoting. " No grain taken from an ancient 

 Egyptian sarcophagus and sown by horticulturists has 

 ever been known to germinate. It is not that the thing 

 is impossible, for grains are all the better preserved that 

 they are protected from the air and from variations of 

 temperature or humidity, and certainly those conditions 

 are fulfiJled by Egyptian monuments ; but, as a matter of 



* De CaniloUe, Origin of CulUvafeil Plants, page 3.54. 



Fig. TI. — Longitudinal seetion 

 of Maize fruit, showing only a por- 

 tion of the endosperm. ep., epi- 

 thelium of seutellum ; per., peri- 

 carp, composed of wall of ovule 

 (nueellus) and ovarian wall united 

 together; pi., plumule; ap., apex 

 of stem ; a. r., adventitious root ; 

 r. c, root cap ; r- s., root sheath. 



