GENERAL REVIEW OP CRYPTOGAMS. 147 



becomes more striking when we compare directly the com- 

 plex structure of the vascular cryptogams, at the top of 

 the scale, with Spirogyra and other simple organisms, near 

 its beginning, and especially when we take into consider- 

 ation the developmental history of plants at the two 

 extremes. Nevertheless, we have been able to recognize at 

 every step, by anatomical features or by other means, the 

 relationship of each group with one or more others. Noth- 

 ing can be clearer than the capital fact that we have not 

 been dealing with isolated forms of life. From lowest to 

 highest, we have found common features that indicate a 

 common origin. 



It will now be well, before proceeding farther, to pass 

 in review the features common to flowerless plants as a 

 whole, comparing them at the same time with what we 

 have seen in our study of the organs of flowering plants. 



While flowering plants are distinguished by the produc- 

 tion of seeds containing an embryo, — that is, a nascent or 

 undeveloped plant, — flowerless plants produce 

 spores. These, like seeds, are bodies from which ^"°^' 

 new individuals arise, but they contain no embryo. They 

 vary to an extraordinary degree in size, form, and structure, 

 but, precisely as in the case of seeds, they are generally char- 

 acteristic of the various groups to which they belong, and 

 are fairly constant in their characters. Thus the spores of 

 mosses are minute, spherical sacs, with a simple membrane, 

 and containing chlorophyll in addition to their other cell 

 contents, while those of ferns are larger, with a double wall 

 and various external markings. Those of the fungi exhibit 

 so many differences that a special chapter would be needed 

 to describe them. In the wheat rust the bright-colored 

 uredospores and septate, dark-colored, and thick-walled 

 teleutospores are so characteristic that they mark at once 



