PH^OPHYCE^E 97 



intercalary transverse divisions. Then follow vertical 

 divisions in greater or less number until the axis, 

 which terminates upwards in a hair, commonly con- 

 sists of tiers of four or more cells. At the base, at 

 least while transverse division continues, the axis 

 remains composed of a single row of cells. The 

 external cells of the upper portion produce short 

 processes which bear cell-rows or sporangia. These 

 branches terminate in hairs, and frequently bear 

 farther branches similarly tipped, which in turn bear 

 reproductive organs or more rarely branches again. 

 The unilocular sporangia are globular or slightly 

 ovate, with a small wart at the apex, and occur 

 singly or in whorls on the axis and branches, being 

 morphologically the equivalent of branches. The 

 plurilocular sporangia are cylindrical and usually of 

 one row of loculi, and are borne singly and in tufts on 

 the short processes of the axis. There are differences 

 of size among them, and this difference indicates a 

 farther one viz., in the nature of the contents. 

 The small sporangia give rise generally to four 

 large gametes, the others six to twelve (commonly 

 eight) gametes. Conjugation takes place only 

 between a large gamete and a small one, and 

 apparently both when they are in a state of mobility 

 and also at the moment of coming to rest. The 

 point of contact is the hyaline part when they are in 

 a semi-mobile state, but when fully mobile there 

 is no general rule in this respect. The large one 

 appears to absorb the small one, and after one to 

 two hours, nothing but the two pigment spots 

 remain to indicate their previous separate existence. 



