DEVELOPMENT OF PLANTS 



179 



the male gametes about the females renders probable the view 

 that some substances as organic acids, etc., are developed in the 

 gametes that serve to draw them together whenever they come 

 within a certain distance of each other. 



The consideration of Colcochaete, a plant of the same order as 

 Ulothrix, has been deferred to this point because it presents 

 several interesting departures from previous types which indi- 

 cate that a higher point has been attained in some respects by 

 this plant than by any other of the green algae. The filaments of 

 Colcochaete have a pronounced apical growth and are usually 

 associated together in a radiate manner, forming small discs or 

 cushion-like masses on the stems and leaves of water plants (Fig. 



Fig. 117. 



Fig. 118. 



Fig. 117. Colcochaete, showing the radiating filaments and hair-like out- 

 growths of the cells. 



Fig. 118. Sexual reproduction of Colcochaete: A, end of a filament 

 bearing the male, an, and female, og, reproductive organs. B, the gameto- 

 spore is being enveloped by the adjacent filaments of the plant. C, gameto- 

 spore germinating. Eight cells have been formed, rupturing the walls of 

 the gametospore. — After Oltmanns. 



