English: Title: Biology; the story of living things

Identifier: biologystoryofli00hunt Year: 1937 (1930s) Authors: Hunter, George W. (George William), 1873-1948; Walter, Herbert Eugene, b. 1867; Hunter, George W. (George William), 1902- Subjects: Publisher: New York, Cincinnati [etc. ] American book company Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book

Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image: 174 ORGANISMS ILLUSTRATING RIOLOGICAL PRINCIPLES

Text Appearing After Image: Great numbers of tiny spores are produced by division of the dense terminal portions of the sporangiophores. As a sporangium becomes mature an outer wall is formed and the spores turn black in color. When this outer wall breaks, the minute spores are scattered far and wide by air currents. Molds also reproduce sexually, by means of con- jugation. Rhizopus has two different strains of mycelia, one of which is called a plus ( + ) and the other a minus ( —) strain. If hyphae of two such strains come in contact with each other, zygo- spores are formed. Short, club-shaped branches are developed from the hy- phae, the dense proto- plasmic tips are cut off from the end of each by cell walls, and these "cells," each of which contains several nuclei, unite to form a zygote. The zygote with the hyphae which develop from it proba- bly represents the diploid stage of chromosome in the life cycle, the haploid stage being reached when the spores on the sporangium germinate. The fungi are of even more interest by reason of their method of nutrition. They are typically neither holozoic nor holophytic, since they live as saprophytes on dead organic materials. This means that they must absorb food materials which are supplied to them from outside sources after digesting them by means of enzymes, when absorption takes place through the plasma membrane of the cell. Alternation of Generations in the Plant Kingdom The most important difference in the life cycle between the Bryo- phytes or Mosses and lower forms, aside from a greater differentiation of the plant body, is the alternation of an asexual with that of a sexual generation in the hfe cycle. The asexual generation, which produces spores, is called the sporophyte, while the sexual generation, which Reproduction in bread mold (Rhizopus nigri- cans). Read the text and then explain the diagrEun.

Note About Images

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 work.