Reproduction of Anyiospetms: Sexual 



The Female Prothallus: The inecasnore germinates m tUm to ght the 

 stage of the plant, as a wholly decadent indlvktoal, parasitic on the parenuJ 



HUB), and produced by 3 mitoses ; represented when functional by 7 Mcfe only, 

 with definite relations, asa minimum organiaatio^moo^todolheworkandno more. 



The original nucleus of the megaspore (embryo-sac) divides, and the daughter- 

 nuclei pass to the micropylar and chalazal ends respectively, there to divide again to 

 s and 4, giving 8 nuclei in all. One nucleus of each group migrates towank the 

 centre of the plasma, and the two fuse, or become closely approximated, as a Central 

 Funonnudfu*. The three left at the micropylar end differentiate as a 

 (sterile), and the functional female gamete or Ootpktn. Th 



film of cytoplasm, but are so far naked cells, with no walls. The synergidae are 

 commonly a little in advance of the oosphere, underneath the micropylar canal, and 

 the nucellus at this point is normally reduced to one cell-layer only. The three 

 nuclei at the chalaxal-end invest with cytoplasm and thin cellulose walls, as definitely 

 osmotic, vacuolated, and absorptive units, nutritive in function, the Antipodal*. 



The Kale ProthaUua: Follows similarly from the germination of the pollen- 

 grain (microspore) on the stigma ; though the first stage mar begin before it leaves 

 the pollen-sac; pollen-tubes pushed out from the grain follow the stylar <anal, 

 absorbing food-supplies from the stylar tissues, these being often p*^^ for the 

 purpose. The growth of the tube is controlled by a htbt-niuUus t produced at the first 

 mitosis, and the other 'generative' nucleus also passes along the tube: the distance 

 travelled in some cases may be considerable, e.g. 10 in., and an inch a day is a Cur 

 rate for the growth of the tube. The latter follows style-canal and placenta! sorfacea, 

 reaching the micropyle of an ovule, and passing along it to the nucellus, apparently 

 under chemical stimulus (chemotropic) ; the last directive stimulus possibly bemc 

 due to the 'synergidae'. Penetration between the cells of the nnceUns is effected 

 mechanically, and the end of the tube is brought into contact with the oosphere. The 

 tube-wall is soft and gelatinous, and the contents of the pollen-tube, 



a nuclei produced by division of the generative nucleus, are passed into the cytoolasm 

 of the embryo-sac. These two nuclei represent the malt gamtta \ and both are 

 functional. The male prothallus is thus a still further decadent, coenocytic, and 

 parasitic individual, represented by 3 nuclei, as the result of a mitoses. 



Fertilisation : One male nucleus attaches to the oosphere, and nuclear fusion 

 (syngamy) takes place ; the other passes on and fuses similarly with the central fusion- 

 nucleus to give a Triple Fusion-nufleus. 



Note. The first fusion is the sexual process, as a union of two specially i 

 sexual units : the second fusion is only a vegetative approximation, since the 

 fusion-nucleus was not a gamete. 



In the fusion of fertilization, the chromosome number is doubled, and the 

 may be termed a DiploidZyg ott ; the latter being capable of growth as a new individual. 



The Zygote (oospore) immediately commences metabolism, the first eff< 

 traced in the secretion of a cellulose wall, and vacuolation of the plasma 

 becomes an osmotic cell, and begins to grow and divide. 



There is no large ovum or motile spermatozoid In such a Higher Plant (although 

 these are typical in many lower forms); fertilization-processes have been greatly 

 simplified, the mechanism being termed sipkcmogamic. 



Formation of Endosperm : the fusion of the second mate nucleus with the 

 central fusion-nucleus, though in no sense sexual, has a 

 and the Triple Fusion-nucleus initiates a series of rapid i 

 of nuclei scattering in the cytoplasm of the embryo-sac, and "spacing oat over the 

 outer wall, as a parietal layer. Cell-walls appear delimiting cell-areas; and in this 

 way, very quickly, a uniform layer of absorbing units is produced, taking food-sop] 



from the nucellus. Synergidae and antipodals are normally soon lost to sight among 



the new cell-formations, and the embryo-sac rapidly enlarges, as does also the whole 



ovule. From the primary system more tissue is produced by rapid 



proceeding inwards, as a thicker and thicker layer ; in the general case " 



enlarged cavity of the embryo-sac with a mass of " 



as a special tract of new tissue parasitically absorptive from the 



