DEVELOPMENT OF PLANTS 279 



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 

 gametospore is not discharged from the plant as in the case of the 

 green or brown algae, but remains permanently in the arche- 

 gonium, where it continues to be nourished by the plant during 

 its germination 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 relationship 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 development 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 importance 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 gameto- 

 spore 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 several weeks, and more important still is the 

 fact that this growth occurs on the land where it is exposed to a 



