544 Transaeiions of the Society. 



reproduced, are due to a hypertrophy of the branches of the plant, 

 •which bear the organs of fructification. They differ from galls, 

 properly so called, which develop on the higher plants, in being 

 pre-existing parts, which have simply undergone an increase in 

 bulk, under the action of the parasite. This exaggeration of the 

 vegetative functions is also often shown by the formation of adven- 

 titious branches at different points of the surface of the gall. 



The exit of the young Notommata born in the galls, and its re- 

 entry into the tubes of Vaucheria to form new galls, is effected 

 through the openings which are spontaneously produced at the 

 summit of the adventitious branches. They also sometimes make 

 use for the same object of the small projection or male organ of 

 reproduction, which persists at the base of the capsule in the form 

 of a tube open at its two extremities. 



