Spores

SPORES (from the Greek sporos - sowing, fruit), cells serving for reproduction. Spores consist of protoplasm, a nucleus, and a membrane. The latter is frequently differentiated into two distinct layers: an inner, thin, colorless or faintly colored endosporium, and an outer, thicker, colored exosporium. In motile spores (zoospores), the membrane is absent. By means of maceration, it is possible to establish that both the inner and outer membranes of certain spores consist, in turn, of several concentrically arranged layers. In the membrane layers of various spores, an uneven development of deposits is observed, resulting in the formation of so-called germ pores. Spores are extremely diverse in their origin. As a result of the development of various methods of sporulation (see Fungi), exospores, endospores, chlamydospores, zygospores, etc., arise. Spores arise either asexually or sexually. Exogenous spores arise through various divisions on mycelial outgrowths—conidiophores (see Fungi). In some cases, a conidium arises in the form of an elliptic or rounded swelling of the terminal part of the conidiophore, which is abstricted, followed by the formation of the next conidium, and so on. With this method of conidium formation, the first of them will be the largest and oldest. In other cases, a conidium arising at the end of a hypha gives rise to several spores, of which the very first will be smallest in size and youngest, or the mycelial threads partially or completely break down into individual cells following the formation of numerous transverse septa, at the site of which increasingly deepening constrictions arise until the complete separation of cells called oidia. One of the features of oidia is their ability to reproduce by budding. Basidiospores arise on special club-shaped cells (basidia), which form short stalks—sterigmata, producing one basidiospore each. The development of endogenous spores is associated with the formation of special receptacles—sporangia (see Fungi). In fungi leading an aquatic lifestyle, spores (zoospores) are formed in zoosporangia, the granular protoplasm of which upon maturation of the sporangia breaks down into individual cells with one or two flagella, serving for movement in water and facilitating dissemination. The number of zoospores ranges from 1 to several hundred. Non-motile spores intended for dissemination via terrestrial pathways are formed in sporangia, or spores develop in a definite number that is a multiple of 2 in receptacles called asci, or bags. In some fungi, the plasma in the hyphae thickens in places, resulting in swellings around which double membranes are formed. These formations have been named chlamydospores; they are classed among survival forms. During sexual reproduction, if two morphologically identical gametes fuse, a zygospore is formed, or, in the presence of sexual differentiation, male cells—antherozoids—fuse with female cells—oospores—forming an oospore. Under favorable environmental conditions, sometimes after a prolonged period of rest, spores germinate.

A. Marrov.