PLA.XT rU01'A(JAT10>J 



8. Plant propagation methods, of which there are many, 

 naturally divide themsehes into two general classes de- 

 I'cndent upon whether seed bodies (spores or seeds) or 

 buds are used. Propagation by spores is so nearly akin 

 to that by seeds that the two are usually classed under 

 the one head — Seedage. Because propagation by means 

 of seeds is dependent upon the previous action of the 



reproductive organs 

 (pistils and stamens) it 

 is called sexual ; that by 

 means of l^uds, in which 

 no such action occurs, is 

 ternjed asexual. This 

 term is also extended to 

 plant reproduction by 

 true and adventitious 

 buds. 



9. Spores are asexual, 

 usually one-celled, repro- 

 ductive bodies of flow- 

 erless plants. A striking 

 difference between them and seeds is that they contain no 

 embr3'0. \Miile reproduction of plants from spores is not 

 dependent on sex, as in flowering plants, the process is, 

 practically speaking, a sexual one. (Compare Seeds, 10.) 



To illustrate, the black or brown spots (called sori) beneath the 

 fronds of many ferns, produce hundreds or thousands of spores. 

 These germinate on moist surfaces and produce small plant bodies 

 (prothalia) each of which develop two distinct growths, an arche- 

 gonium and an antheridium, which correspond respectively to the 

 pistils and the stamens of flowering plants and are, therefore, the 

 essential organs of reproduction in flowerless plants. When, during 

 the process of growth, an antheridium unites with an archegonium, 

 a sperm cell from the former fertilizes the egg cell in the latter and 

 a little plant is produced — a fern, a moss, a mushroom, or some other 

 flowerless plant, according to the species. 



Spores are of interest to the horticulturist because they produce 

 ferns, mosses, mushrooms, fire-fanging fungi (137), and many 

 plant diseases such as apple scab, wheat rust, black knot of cherry 

 and plum, downy mildew of grape, etc. 



FIG. 4 — CRACKED SOIL 



Bad physical condition due to laclt of 

 vegetable matter. Such soil dries out deepiy 

 because of the craclcs. 



