SECT. I 



CRYPTOGAMS 



355 



yellowish-green, oil-ronuing cliloroplasts, and the formation of zoospores with cilia 

 of unequal lengths (in many Confervao tlie zoospores have only a single ciliuni). 

 In addition to zoospores thick-walled aplanospores arise by the seimration by the 

 cells of the filament. 



The majority of the Heterocontae have uninucleate, only occasionally bi-nucleate 

 cells. But there are some genera with multinucleate cells in the class, e.g. 



OpliiQcytiuvi and Sciadiiwi. 



On this account, with some 

 reservation, Oltmanns also 

 places here Boh-ydnim granu- 

 latum (Fig. 27'2), which was 

 formerly included in the 

 Siphoncae. This Alga is 

 cosmopolitan and grows on 

 damp clayey soil, where it 



Fig. -Til.— Conferva bomhycina. 1, FiUimeiit ; '2, 3, formation 

 of transverse wall (fy) in cell division ; 5, formation of 

 aplanospores by breaking down of the llUunent ; 10, 

 Zoospores with cilia of unequal length. (After Gay 

 (7, 5), BoHLiN (5, 3), Luther (10). From Oltmanns' 

 Algae.) 



Fl(i. 272.— .4, B, Botrydium granu- 

 latum. A, The whole plant ; 

 B, Swarm - spore. (A x 28 ; 

 B X 040.) 



forms groujis of green, balloon-shaped vesicles about 2 mm. in size. These are 

 attached to the soil by branched colourless rhizoids. The whole plant coiTesponds 

 to a single multinucleate cell ; its protoplasm contains numerous green chloroplasts. 

 The zoospores, produced in large numbers by the division of the contents, esca2)e 

 by an opening at the summit. Each has a single cilium and contains two 

 chloroplasts. After swarming the spore surrounds itself with a wall and grows 

 into one of the balloon-shaped plants (i). 



In some genera, gametes resembling the zoospores but conjugating in pairs 

 have been observed. 



2 A 1 



