Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor.

  • Strasburger, Eduard, 1844-1912.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor. Source: Wellcome Collection.

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    consider the small cell as the vegetative one; in point of fact, however, it is the generative cell, and it is its moi’e deeply stain- ing nnclens which effects fertilization.®—These observations can, as far as the youngest stages are concei-ned, be carried on in pure water ; for the oldest stages we must bring acetic methyl-green or acetic iodine-green to our aid.—The species of Leucojum [Snow- flake] agree with Tradescantia. The Crown Imperial, Fritillaria imperialis, presents another favourable object for investigation. In sections of alcohol material, lirst placed in water, and then stained with logwood, the two nuclei in each pollen-grain can be seen very beautifully. If we open a bud of CEnothera hien7iis [the Evening Pi’imrose] which is ready to expand, we shall find that the anthers have already dehisced and set free their pollen. These latter are suspended between the anthers by cobweb-like threads. If such threads are stretched out upon an object-slide, they appear under the micro- scope as exceedingly delicate threads, partly stretched straight, partly tangled. The pollen-grains in a dry state are opaque, but their three-cornered form is at once noticeable. In water, with stronger magnification, they show as flattened, symmetrically triangular bodies, with rounded projecting angles. At the base of each of these rounded corners an annular thickening of the mem- brane of the pollen-grain is to be seen. The contents of the pollen- grain appear finely granular; the two nuclei are only recognisable in the contents of the ripe grain with extreme difficulty. In sulphuric acid the pollen membrane assumes a red-brown colour. By it an outer, thin, yellow-coloured layer is raised from the body of the pollen-grain, forming folds upon an inner, thicker, red-brown layer. Both layers coalesce in the wall of the corners. From the side walls of the corners fine teeth project inwards, so that these walls appear as if porous. The apex of the corners is dissolved by the sulphuric acid. The fine threads, binding the pollen-grains together, resist water, sulphuric acid, and potash, and are insoluble also in alcohol. If the grains are treated wdth 25 per cent, chromic acid, their membrane is soon dissolved, and in all cases the strongly cuticularized portion somewhat earlier than that which is either not, or but slightly cuticularized, which remains for a time as colourless swollen caps on the projecting corners of the plasmic contents. Later on, these also are dissolved; and ultimately even the cobweb threads between the grains do not resist the chi-omic acid.—From the stigma of an older flower pollen-grains can be