FERTILITY 



or remain to bo evaporated. The aim should be to so 

 prepare the land by sulidrainnsi-. plowing and surface 

 tillaffp. and bv intrc^hii-ini; at l.a^r one eropof tap-rooted 

 plants in tlir rotation, tliat tlir surplus water will filter 

 tlinMii;li till- soil in a nasonabk- time. Percolation of 

 rainwater through soils nialii's them more friable and 

 warmer in spring, aerates the land, promotes beneficial 

 ,nd ch« 

 itrogenous compounds contained in 

 Soils which are reasonably porous have the power of 

 retaining more moisture, and of giving it up to plants 

 when needed to a greater extent, than either open sandy 

 or close clay soils do. Fertility, which results in fruit- 

 fulness, is governed very largely by the water and mois- 

 ture conditions of the soil, and these, in turn, are largely 

 governed by the texture of the land and the amount of 

 humus which it contains. 



Legumes, used either as a harvest or cover-crop, pro- 

 mote fertility. A cover-crop of clovers planted August 

 1, and analyzed (ii days after planting, contained of 

 nitrogen, in roots and tops, per acre as follows: 



Tops Roots Total 



p—r 



Lbs. 



Clov 



be used i 



I fix and store 



ind • 



make available ili, . -.1 , , n-ntn.-nts or the lauM, 

 thereby greatly inei-. , -ii I n \ of the soil. 



Barn manures. «le ■, ■ •! . i -.iv,! r.,r an,l intelli- 

 gently applied, not oiii;, ii.nii~i[ iieeeptalile plaiit-food 

 but humus as well. Fertility and high productivity 

 usually may be maintained many years by means of su- 

 perior tillage, leguminous harvest and cover-crops, and 

 the manures of the farm. In some cases a high state of 

 fertility can be maintained only by occasional applica- 

 tions of commercial mineral fertilizers, as phosphates 

 and potash, but too often expensive fertilizers have been > 

 substituted for tillage, leguminous plants and barn 

 manures. 



Fertility may frequently be promote.l by liu-ht n|ipli- 



may serve to make plant-food more a\ailali]i . imi'rove 

 soil" texture ami correct acidity. Its use is is[ierially 

 recommended on clay and moist lauds and in orchards 

 where the ground is much shaded. Applications of gyp- 

 sura and salt are sometimes beneficial in maintaining 

 fertility, but they, as well as lime, usually act indirectly, 

 as the soil is seldom deficient 

 in these constituents so far as 

 they are required as plant- 

 food. On high-priced lands, 

 especially those devoted to 

 horticulture, the s.iil si,,,,,!.! 

 be made and kept fertile- •. 

 up to its highest pro.lu.n 

 power. 



Sometimes soils are rendered 

 unfruitful by the presence of 

 deleterious substances, as or- 

 ganic acids or alkaline salts, 

 or a superabundance of some 



ful ingredients, as water or 

 nitrogenous matter. An ex- 

 cess of nitrogen stimulates the 

 growth of stalk and straw at 

 the expense of grain, or in the 

 orchard it tends to the for- 

 mation of wood rather than 

 to fruitfulness. The acidity 

 should be corrected by lime, 

 as noted above, the surplus 

 water removed by drainage, 

 the nitrogenous matter re- 

 duced by the production of 



such crops as are not harm- imcieus. -uagniueu juu 

 fully afi'ected by its super- diameters. 

 abundance, such as forage 



crops which are prized for their foliage rather than for 

 their seeds, while the alkalinity may sometimes be over- 

 come by deep tillage or irrigation. i. p. Roberts. , 



FERTILIZATION 



FEETILIZATION. The union of 

 male cell and a female cell, to form a 

 of growing into a plant. The term v 

 to include the transfer of pollen to 

 Darwin's "On the Fertilization of ( nr 

 but this process is now generallx ili~i 

 Unafion, which see. In the 

 lower plants, fertilization can 

 be much more readily ob- 

 served than in the seed plants, 

 because in the latter it takes 

 place inside of opaque parts, 

 and therefore can be studied 

 only by the most careful mi- 

 croscopical methods. The 

 process of fertilization is here 

 described as it occurs in lilies. 

 In other seed plants it differs 

 in details. 



The generative cell (g. Fig. 

 814) is produced by the pol- 

 len grain before it leaves the 

 anther. It is usually lenticu- 

 lar, and placed at one end of 

 the grain. Its most important 

 part is the spherical nucleus, 

 which occupies the ceuter. 

 When the pollen grain is con- 

 veyed' to the stigma (s, Fig. 

 81o), the larger cell [f. Fig. 

 814), nourished by food it ab- 

 sorbs from the stigma, grows, 

 forming a long tube (pt, Fig. 

 815), which traverses the nar- 

 row triangular canal (1, 2. 3, 

 Fig. 815) that leads down the 

 long style to the ovary. In 

 many plants the style is not 

 hollow. In this case, and often 

 when it has a canal, the pollen 

 tube pushes its way between 

 the cells of the style, living 

 on the food it absorbs. About 

 the time the tube begins to 

 grow (or later) the generative _ _ _ 

 cell divides into two. These e„t i^^gt^. 

 male cells, or sperms, migrate through the 

 down the tube {pt, Fig. 815), 

 which makes its way into the 

 opening between the inner in- 

 tegument (!, Fig. 816) of the 

 ovule, penetrates the body of 

 the ovule and enters the em- 

 bryo-sac (E. Fig. 816). Its 

 direction of growth is deter- 

 mined by substances, proba- 

 bly chiefly the sugars, con- 

 tained in the parts which it 



While the pollen tube has o 

 been growing, the female cell 

 has been forming in the embry 

 The nucleus of this huge cell, "li: 

 vided into two, these into four. 

 nuclei, four migrating to eaeh 

 each group advances toward the i 

 the two fuse into one {r, Fig. slln 



stigma on which pollen 

 grain, p, has been lodged. 

 The course of the pollen 

 tube, pt, is indicated by 

 broken line. At the right, 

 1,2,3,4. are cross sections 

 of the pistil at the levels 

 indicated by the arrows : 

 1, the stigma: 2, 3, the 

 style, show the triangular 

 canal which leads into the 

 three chambers of 4, the 

 ovary, in each chamber 

 of which are two rows of 

 o\-ules. Natxu-al size. 



(A-, Fig. 816). 

 siiii.^]e. has di- 

 e,e into eight 

 lleii one from 

 of ilie sac and 

 ^Toui. id' three 



814. A pollen grain of 

 Lilium Philadelphicum. 

 Before le.-iving anther, seen 

 in section : (, the tube 

 cell ; //, the generative 

 cell. The large spherical 



od:a end of the emlirvo 's;e- ul . Fiu'. sU'.i. In the 

 lilies. ho«vver, tliis do/s not i,'o tar, :,ml two of the 

 three antipodal nuclei are seen to be i,lre:i<ly reduced in 

 size and partially disorganized. They have no further 

 history. The group of three nearest the point of en- 

 trance of pollen tube accumulate the living protoplasm 

 about them and thus organize three naked cells. Two 

 of these (called svnergidae) usually begin to disor- 

 ganize before the pollen tube reaches them, but may 

 persist until then or even later. In the lilies they usu- 

 ally disappear early. The third is the egg, or oosphere. 

 When the pollen tube enters the embryo-sac, its end be- 

 comes softened and bursts, permitting one or both of 

 the male cells to migrate from 



One male nucle 



