. Elementary botany. Botany. CHAPTER XXXIV. }AMETOPHYTE AND SPOROPHYTE OF ANGIO- 450. Male prothallium of angiosperms.—The first division which takes place in the nucleus of the pollen grain occurs, in the case of trillium and many others of the angio- sperms, before the pollen grain is mature. In the case of some specimens of T. grandiflorum in which the pollen was formed during the month of October of the year before flowering, the divi- pig. 297. J °7 Nearly mature sion of the nucleus into two nuclei took place pollen grain of tril- . Hum. The smaller soon alter the formation 01 th
. Elementary botany. Botany. CHAPTER XXXIV. }AMETOPHYTE AND SPOROPHYTE OF ANGIO- 450. Male prothallium of angiosperms.—The first division which takes place in the nucleus of the pollen grain occurs, in the case of trillium and many others of the angio- sperms, before the pollen grain is mature. In the case of some specimens of T. grandiflorum in which the pollen was formed during the month of October of the year before flowering, the divi- pig. 297. J °7 Nearly mature sion of the nucleus into two nuclei took place pollen grain of tril- . Hum. The smaller soon alter the formation 01 the four cells from cell is the genera- . tiveceii. the mother cell. Ihe nucleus divided in the young pollen grain is shown in fig. 297. After this takes place the wall of the pollen grain becomes stouter, and minute spiny projections are formed. 451. The larger cell is the vegetative cell of the prothallium, while the smaller one, since it later forms the sperm cells, is the generative cell. This generative cell then corresponds to the central cell of the antheridium, and the vegetative cell perhaps corresponds to a wall cell of the antheridium. If this is so, then the Germinating spores male prothallium of angiosperms has become (pollen grains) oi pel- 1 ° 1 tandra; generative reduced to a very simple antheridium. The nucleus in ne undi- r . . r - .... vided, in other divided farther growth takes place alter fertilization, to form the two sperm In some plants tin- generative cell divides into n,uclei-; vegetativenu- 1 ° 1 lens in each Dear the the t\v sperm cells at the maturity of the pollen grain. pollen grain. In other cases the generative cell divides in tin- pollen tube after the germination f the pollen grain, for stud)- >>t' the pollen tube the pollen may lie germinated in a weak solution of sugar, or on the cut surface 228. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration a
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