1222 



FERTILIZATION 



FERTILIZERS 



//-i 



course the poUen-tube is doubtless "directed" by the 

 distribution of food. Meanwhile, the generative 

 nucleus of the pollen-tube divides into two sperm 

 (male) nuclei, and these migrate to the growing end 

 of the tube. 



With the formation and 

 opening of the flower, the 

 embryo-sac attains its devel- 

 opment. This structure is too 

 complex to require full treat- 

 ment here, but it is sufficient 

 to say that, when approaching 

 maturitj', it consists of one 

 large cell containing eight 

 nuclei, four of which collect at 

 each end of the cell. One 

 nucleus from each end marches 

 to the center, and the fusion 

 which then commonly results 

 gives a nucleus the divisions 

 of which ultimately organize a 

 so-called food, or endosperm, 

 tissue, which may surround the 

 embryo when formed. 



At the micropylar end of the 

 embryo-sac, another nucleus 

 organizes the egg-cell — a 

 prominent cell with consider- 

 able protoplasm — and the other 

 two degenerate or form the 

 subsidiary cells of an "egg ap- 

 paratus." The cells at the an- 

 tipodal end of the embryo-sac 

 are also of little present sig- 

 nificance. At about the time of 

 the maturity of the egg-cell 

 the tip of the pollen-tube 

 reaches and penetrates the wall 





^^ 



k 



& 



2 



3 



1496. Outline of a pistil of 



Lilium philadelphicum. 



A lengthwise view of pi.stil of the embryo-sac, then dis- 

 almost through the center; solves and liberates the two 

 s, sugma on which pollen- y nuclei. One of these fuses 

 grain, p, has been lodged. .,, ^, ,, i ii • • 

 The course of the pollen- With the egg-celi, and this IS • 

 tube, p(, is indicated by the important act under con- 

 broken line. At the right, sijeration. The other sperm 



1, 2, 3, ft, are croas-sections , j., ^ -.l xl 



of the pistil at the levels nucleus often tuses with the 



indicated by the arrows: /, endosperm nucleus, but that 



the stigma; 2. S. the style j^gg ^g^ ^ffg^^ ^j^g characters 



snow the triangular canal ^ ,, , rr», ^ . f. 



which leads into the three ot the embryo. J. he lUSlon Ot 



chambers of 4. the ovary, in egg and male nucleus unites, 



each chamber of which are „„ tUp ntbpr hanH tVip fhnnc- 



two rows of ovules. (Nat- on tne otner nana tne cnarao- 

 ural size.) tcrs of the ovule-bearing and 



pollen-bearing plants in the 

 fertilized egg, which may proceed immediately to 

 develop the embryo. B. M. Duggab. 



FERTILIZERS. It is now well recognized that 

 shade trees, ornamental shrubs, small fruits, and 

 flowering perennials, as well as annual flowering and 

 foliage plants, are often as greatly benefited by the 

 use of proper fertilizers and manures as vegetables and 

 ordinary farm crops. There are, nevertheless, occa- 

 sional soils on which fruit trees, and shade trees in 

 particular, require little or no artificial fertilization or 

 manuring. For example, it was not found profitable 

 to fertilize apple trees at the Agricultural Experiment 

 Station in Geneva, New York, whereas at the Pennsyl- 

 vania Agricultural College the use of fertilizers was not 

 only strikingly helpful, but practically vital to success- 

 ful orcharding. Instances of such contrasts in con- 

 nection with trees and shrubs are always to be expected. 

 On this account the giving of rulc-of-thumb directions 

 for fertilizing, in a work of reference which is designed 

 to be generally applicable to the entire United States, is 

 not only well nigh impossible, but may, if followed, 

 lead to the most unreasonable procedure on the part 

 of those not sufficiently conversant with their own 



particular soil conditions. For this reason this dis- 

 cussion will be confined largely to the general principles 

 involved, since they not only fail to mislead the novice, 

 but may serve as a safe and rational basis for general 

 procedure for all. 



Shade trees, ornamental trees and. shrubs. 



Because of the fact that trees have an extensive 

 root-system, and hence possess a wide feeding range, 

 they often stand less in need of artificial manuring 

 and fertilizing than certain shrubs, especially if the 

 latter have already been set for a long time. 



It is to be presumed that most soils contain enough 

 iron and magnesia to meet the needs of trees and shrubs, 

 yet since these substances are just as essential to their 

 growth asanyof the three so-called "essential elements," 

 it is well to bear in mind that very rare cases may be 

 met with in which even iron or magnesia may be help- 

 ful. In this connection it may be mentioned that the 

 soil in a section of northern Michigan is said to con- 

 tain so little iron that certain farm animals, if fed exclu- 

 sively on the plants which grow there, cannot be 

 reared successfully. It has even been found that 

 manganese compounds are sometimes helpful to plants, 

 and if the supply of iron is insufficient, they aid in pro- 

 moting chlorophyl formation in the leaves, without 

 which the higher plants cannot exist. 



Some soils are relatively deficient in magnesia as 

 compared with lime, and when such is the case, growth 

 is likely to be restricted until enough magnesia is 

 added to create a proper balance between the two. A 

 much more frequent lack, in soils of the humid regions, 

 is lime. 



Unfortunately, an extended and systematic study of 

 the lime requirements of trees and shrubs has not yet 

 been made, although many valuable isolated observa- 

 tions are on record. It 

 would be of great value 

 if such experiments 

 were conducted on an 

 extensive scale. Such 

 experiments as were 

 made in this direction 

 in Rhode Island 

 showed, for example, 

 that the American 

 elm ( Ulmus ainericana) 

 and the basswood 

 (Tilia americana) were 

 both greatly helped by 

 liming when grown on 

 the very acid granitic 

 soil of that state. 

 From this it may be 

 inferred that benefit 

 from liming would also 

 follow on many of the 

 soils of the humid re- 

 gions which are derived 

 chiefly from granite 

 and from certain of 

 the sandstones, shales, 

 slates, gneisses, schists 

 and conglomerates. 



The sugar or rock 

 maple was found to be 

 but little helped by 

 lime, even where the 

 elm and basswood 

 showed striking bene- 

 fit. The common white 

 birch seemed to be 

 even less responsive to 

 liming than the sugar 

 maple. 



The use of much 



1497. Section of an ovule of 

 Lilium philadelphicum. 



Cut lengthwise: i, i, inner integu- 

 ment, inclosing except at a narrow 

 orifice (micropyle) where the pollen- 

 tube, p^ enters the body of the ovule, 

 which is chiefly occupied by the large 

 embryo-sac with three nuclei, one 

 much disorganized, e, the endosperm 

 nucleus, just being formed by fusion 

 of two nuclei from the respective ends 

 of the embryo-sac. a", male nucleus, 

 which has just migrated from pollen- 

 tube and is about to fuse with 9 , the 

 egg nucleus. The synergidse, or "egg 

 apparatus," have disappeared. (Mag- 

 nified 670 diameters.) 



