The Origin of Land Plants 101 



be found in some of the large algae, like the great 

 kelps, and also in various mosses, they never reach 

 the perfect development that distinguishes them in 

 the sporophytes of the ferns and seed-plants. 



The Root of Pteridophytes. With the develop- 

 ment of the primary root, which, unlike the hair-like 

 " rhizoids " of the gametophyte, is a massive struc- 

 ture capable of extensive growth and admirably 

 fitted for the absorption of the water from the soil 

 and its transportation to the different organs of 

 the sporophyte, the independence of the sporophyte 

 is for the first time perfectly established; and we 

 have henceforth to deal with plants which are not 

 modifications of an originally aquatic type, as is the 

 case with the gametophyte, but are elaborations of 

 a structure, the zygote or resting spore of the algae, 

 which is from the beginning a structure adapted 

 to terrestrial conditions. This probably accounts 

 for the perfect adaptation of the sporophyte to ter- 

 restrial life, when compared with the indifferent suc- 

 cess as land plants of even the most perfect gameto- 

 phytic structures, like those of the larger mosses. 

 The latter, owing to their failure to develop an ade- 

 quate root system, seem to have about exhausted 

 the possibilities of the aquatic gametophyte, and the 

 further development of the vegetable kingdom is 

 mainly bound up with the amplification of the ter- 

 restrial sporophyte. With the inauguration of this 

 entirely new plant type begins the most important 

 chapter in the history of the vegetable kingdom. 



