SPORES AND THALLIDIA. 



17 



the filamentous organism Vaucheria produces a single comparatively large green 

 spore in each of the club-shaped outgrowths developed by the tubular branches of 

 the plant, and each spore thus formed is able, when free, to swim about by means of 

 its numerous short cilia. On the other hand, the mould-like Saprolegniacese, which 

 live under water upon decaying animals, develop a large number of colourless 

 spores in their clavate filaments, and these after escaping from the tubes whirl 

 about in the water by means of two long revolving cilia (c/. fig. 192). In both 



Fig..l92.— Swarm-spoies of Saprolegniacese and Chytridiacese. 



1 Aehlya prolifera. -, 3, < Development and escape of swarm-spores of Achlya prolifera. * Chytridium Ola parasitic upon the 

 oogonium of CEdogoniurn; development and escape of swarm-spores. '^ Saprolegnia lactea. 7 Development and escape of 

 the swarm-spores of Saprolegnia lactea (partly after De Bary and Pringsheim). ix20; 2, s^ 4x400; 6x300; «xlOO; 7x300. 



these instances the spores themselves possess the power of movement and of 

 swarming about in water, whence they are called "swarm -spores". The name 

 " zoo-spores " {^(hov = animal) has also been applied to them on account of their 

 decided resemblance in form and behaviour to certain Infusoria. 



The delicate, profusely-branched mycelia of the Moulds, included under the 

 name Mucorini, give rise to special filaments which grow straight upwards. These 

 erect hyphas divide into two cells. The upper cell becomes a spherical bladder, 

 and the under a long slender stalk, the upper end of which protrudes in the form 

 of a hollow stopper into the bladder supported by it (cf. fig. 193 ^). The protoplasm 

 in the upper vesicular cell breaks up into a large number of spores and thus 



VOL. II. 



52 



