PROPAGATION, DEVELOPMENT, AND CULTURE. 21 



which, lies upwards produces the rudimentary stem. The 

 spores are very minute vesicles of various shapes, but 

 mostly roundish, and are often beautifully ornamented with 

 markings on the exterior. They consist merely of a small 

 vesicle of cellular tissue, and as they grow this vesicle 

 becomes divided into others, which again multiply and 

 enlarge, until they form a minute green leaf-like patch, 

 roundish but irregular in outline, unilateral, and often, if not 

 always, two-lobed, forming a primordial scale or leaf ; this 

 by degrees thickens at a central point on the side, which 

 henceforth becomes the axis of development, and from this 

 point a small leaf or frond is produced on the upper surface 

 where the tissue is acted on by light. This leaf is usually 

 very different in aspect as well as size from the mature 

 fronds, and is succeeded by other fronds, which acquire by 

 degrees the characteristic features peculiar to their species. 



In some annual Ferns the mature character is soon at- 

 tained, but in others two or more years of growth is re- 

 quired before they reach maturity; they, however, soon 

 begin to assume something of their peculiar appearance, 

 so that by the time three or four of these young fronds 

 are produced, sometimes even earlier, a practised eye can 

 recognize the species. 



