DEVELOPMENT OF PLANTS 265 



(e) Noteworthy Departures in the Life History. — It should be 

 stated that the gametophyte of certain species of the Marchan- 

 tiales may live for long periods without producing the gametes. 

 In fact, it frequently multiplies by means of buds and branches 

 which become detached and grow directly into new plants. How- 

 ever, as soon as conditions are favorable the sexual organs and 

 gametes will appear. There are several features in this history 

 that must be kept clearly in mind. In the first place, the gameto- 

 spore is not discharged from the plant as in the case of the green 

 or brown algae, but remains permanently in the archegonium, 

 where it continues to be nourished by the plant during its germi- 

 nation and the formation of its spores. Therefore, it develops 

 essentially as a parasite upon the plant, as is the case among the 

 red algae. This retention and nourishment of the germinating 

 gametospore in the plant is perhaps the most important of any of 

 the variations that appear in plant life. Owing to this relation- 

 ship the gametospore attains a larger growth with increased 

 power of spore production. In Ricciocarpus the capsule is about 

 500 times as large as the gametospore. In this way the develop- 

 ment of many new plants is made possible by a single fusion of 

 gametes. This is a very significant feature in terrestrial plants, 

 since the fusion of the gametes is effected with more difficulty, 

 owing to the absence of aquatic conditions. Without doubt this 

 change was induced by the transference of foods from the sexual 

 to the asexual plant derived from the gametospore. This loss of 

 food gradually prevented the sexual plant from producing spores 

 or other bodies designed to multiply its numbers and we will 

 finally see that the sole work of the sexual plant is limited to the 

 production of gametes. Note also that the gametospore not only 

 has a larger growth but a longer life. This is of the utmost im- 

 portance because it became exposed in this way to a new series 

 of stimuli that affected it profoundly and that resulted in the 

 evolution of the higher types of plants. Among the green algae 

 the actual germination of the gametospore is limited to a few 

 hours at the most and this is effected in the water, where the 

 conditions are exceptionally uniform. The germination of the 

 gametospore in the case of the liverworts is prolonged over sev- 



