Page:The New International Encyclopædia 1st ed. v. 18.djvu/542

* SPOKE. 466 SFOKOZOA. cese, q.v.) the spores liave no cilia and hence can- not swim, and as each sporangium produces four such spores they are called tetraspores. Among the fungi, asexual spores, which are produced in great profusion and variety, have received many names. Among the alga-liUe fimgi (Phycomycetes, q.v.) they are developed in one- celled sporangia, and are mostly light, dry cells, easily scattered by wind. Such are called simply spores, with no designating prefix. Among the sac-fungi (Ascomycetes, q.v.), however, two con- spicuous forms of asexual spores occur: the one, conidia, which are successively cut ofl' from the tip of a filament, often forming chains; the other, ascospores (fig. 4), developed within a delicate sac (ascus). Among the rusts (Uredi- nales, q.v.) the greatest variety of asexual spores for one plant is reached ; e.g. in wheat nist there are foiu'. Among toadstools (Basidiomy- cetes, q.v.) the characteristic spores are basidio- spores, borne two or four together on the tips of pointed branches from a swollen filament, the basidium (fig. 8). There are several other spores of minor significance among the fungi, each with its distinctive name. Among the bryophytes (liverworts and mosses) and most of the ptcrido- phytes the asexual spores are called simply spores. In heterosporous plants (some pterido- phytes and all spermatophytes), however, there are two kinds of asexual spores, megaspores or macrospores and microspores (qq.v. ). Before their character in seed plants was appreciated these two kinds were called respectively embryo-sacs and pollen-grains. In all of these wind-dispersed asexual spores, the spore-wall consists of two lay- ers, a delicate inner one (intine or endospore) and a tough outer one (exine or exospore), often variously sculptured, especially in the pollen- grains of flowering plants, and sometimes even winged, as in the pollen-grains of pines (fig. 2). Sexual Spores. Only two names, zygospores and zygotes, are used to designate sexual spores which result from the union of similar gametes (fig. 5, 7). (See Isog.my.) Oospores, pro- duced by all but the lowest plants, are formed TYPES OF SPORES. 1. Megaspore of Selaginella : 2. microspore (pollen) of pine; 3, spore of Equisetum with elaters, 4, aecospore of liclien; 5, zogospore of .Spirog.vra; 6. zoospore of Vau- cheria: 7, zygospore of Mucor; 8, baaidiospores; 9, zoospores of green alga. by the inion of dissimilar gametes (see Hetero- gamy) known as sperms and eggs (obspheres). See Sex in plants. Under suitable conditions any spore begins toi form a new plant, the process being called germi- nation. In some cases the germination is imme- diate; in others it is delayed for a longer or shorter period by unfavorable conditions, as in winter. Spores adapted to delayed germination are called resting spores, and may be recognized by their unusually heavy protecting wall. See Keproduction. The methods of spore dispersal are as diverse as the various means of seed dispersal. In many of the lower forms, as in the alg* and some fungi, zoospores may distribute the species over wide areas. Most aerial spores are light and usually small, and are thus readily scattered great dis- tances by wind, a fact evidenced by the usually early appearance of ferns on new tropical is- lands. Jlechanical expulsion and special devices for separating or entangling spores, as the ela- ters of Equisetum (fig. 3), are common. SPOREK, spe'rer, Gustav Friedkich Wil- uelm (1822-95). A German astronomer, born in Berlin and educated there. He taught at Bromberg. at Prcnzlau, and at Anklam (since 1849). Here he began in 18G0 to observe sun spots with the view of determining the law of solar rotation. Through a Government endow- ment a solar observatory was erected bj- Iiim at Anklam. SpiJrer arrived independently at a con- clusion similar to that of Carrington concerning the equatorial quickening of the sun's movement on its axis. In 1808 he took part in an expedition to East India for observing a total eclipse of the sun. The structure of the chromo- sphere was also investigated by Sporer. This showed the chromosphere to be of the same na- ture as the vast protrusions from it. From 1874 to 1894 Sporer was observer at the astrophysical observatory at Potsdam. SPOROPHYLI. (from Gk. airopoi. sporos, seed + 0!)XXo>', phi/Uon, leaf). A leaf-like organ that occurs only in spermatophytes and in cer- tain pteridophytes and bears sporangia (spore- cases). Though generally unlike ordinary foli- age leaves in appearance, they are regarded as foliar organs. See Sporangium. SPOKOPHYTE (from Gk. ajrdpos, sporos^ seed + 4>vt6p, phi/ton, plant). The sexless phase in alternation of generations (q.v.). SPOKOZOA (Neo-Lat. nom. pi., from Gk. ff7r6poi, sporos, seed + f<?o», :::don, animal). A class of parasitic protozoa comprising the ma- laria germs, Texas cattle-fever germs, etc. While the sporozoa difi'er much in structure, they are similar in parasitic habits and development. As a rule they are more or less oval or elongated, with no organs of locomotion except in the early stages. They are very minute, though Greriaruia gigantea, which lives in the intestine of the Eu- ropean lobster, is of comparatively colossal size, being a little over half an inch in length. They are nourished by the absorption of the fluid in which they live. The young arise as 'sporoblasts,' which when enveloped with a membrane are called spores, the contents of which break up into sev- eral small bodies or 'sporozoites'; the latter to complete their development must leave the first host and enter a second one. Some of the sporozoa are parasites in the in- terior of cells, such as those lining the intestine of higher animals. Malaria in man has been proved to be due to the presence of a sporozoan