. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 364 GERMINATION OF POLLEN cell sooner or later follows suit (Fig. 215, C). The former usually remains undivided, whilst the latter ultimately produces two male nuclei (cf. below). In its downward growth the pollen hibe is sometimes nourished by the secretion of papillae forming a continuous lining to the canal or canals traversing the style and extending uninterruptedly into the loculi of the ovary { Tulip and Violet). In many cases, however, the style is solid, the pollen tube penetrating through the axi
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 364 GERMINATION OF POLLEN cell sooner or later follows suit (Fig. 215, C). The former usually remains undivided, whilst the latter ultimately produces two male nuclei (cf. below). In its downward growth the pollen hibe is sometimes nourished by the secretion of papillae forming a continuous lining to the canal or canals traversing the style and extending uninterruptedly into the loculi of the ovary { Tulip and Violet). In many cases, however, the style is solid, the pollen tube penetrating through the axial core of thin-walled tissue, nourished by the sugary sap which the latter contains. In some cleistogamic. Fig. 213.—Diagrams illustrating normal fertilisation (porogamy, A) and chalazogamy (B). , embryo sac ; m., micropyle ; ii., nucellus ; pi., pollen tube. flowers { Purple Deadnettle) the pollen grains germinate in the anthers, and the pollen tubes grow from there to the stigma. The period of time occupied by the pollen tube in growing down to the ovules varies greatly in different species, and bears no relation to the distance to be traversed. In the Crocus, where the style is 6-10 cm. long, the interval is only from one to three days, whilst in the Meadow Saftron {Colchicmn), with a style of about the same length, it is six months (from autumn, when polhnation occurs, to the following spring). A similar prolonged interval not uncommonly obtains in woody plants { Hazel), though the distance traversed is short, and in some Oaks the ovules do not even commence development until after. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
