Reproduction and Germination. 39 



classed as somatic reproduction, or as specialized instances of 

 growth. 



Eggs of the higher plants are generally retained in the ovary 

 until they have developed into an embryo, in which the main 

 axis of the new individual is differentiated in different stages, 

 according to the species. The embryo is generally protected 

 by coatings of resistant tissue, and may have stored in its own 

 cells a quantity of reserve food before its connection with the 

 parent plant is severed. The awakening of the embryo, con- 

 stituting the germination or sprouting of the seed, may also be 

 regarded as a specialized form of growth, since the method of 

 nutrition in the earlier stages of the 

 seedling are entirely different from 

 those of the adult plant. 



The propagation of a plant from a 

 part of the body, such as a fragment 

 of a stem or leaf, is accompanied by 

 regenerative processes, the develop- Fig. 20 . Germinating 



, spores of Schizcea pusilla. 



ment Of. Callus and Other protective After Britton and Taylor. 



tissues over cut surfaces, and the 



formation of new growing layers. Propagation, therefore, is 

 also a specialized method of growth, widely different in mean- 

 ing and final effect from reproduction by spores and eggs. 



32. Germination of spores. Take a small fragment 

 of soft brick, and boil it thoroughly to kill all organisms at- 

 tached to it. After it has been in the water for an hour, re- 

 move and set in a saucer of spring water. Cover with a large 

 tumbler. After the brick is cool, sprinkle the spores from the 

 opening sporangia of some fern liberally over it. Replace the 

 tumbler, and set the preparation aside for three or four weeks. 

 After this period, examine it frequently. As soon as some of 

 the small greenish prothallia are seen, scrape off some of the 

 material from the brick, and examine with a magnification of 

 sixty to four hundred diameters. Make a series of drawings 



