22,2 Shaw: Merrillosphaera africana 195 



in the somatic layer; in fact, there appears to be a pair of such 

 vacancies, of the sort that mark antheridial sites. 



Specimen 13. — Plate 3, fig. 17. This coenobium contains 

 thirty-one oospores by count under the microscope. There ap- 

 pears to be an antheridial site a little above and near the center 

 of the picture. Examination from the back of the slide revealed 

 a similar vacant space on the opposite side of the. coenobium. 

 There is a similar vacancy halfway to the left side and a little 

 below the middle of the coenobium. It is obscured by a spore 

 directly behind it on the opposite side of the coenobium. The 

 oospores have smooth walls of about 41 /* in outside diameter and 

 about 2 p. in thickness, and contain a protoplast of which the 

 denser portion is about 33 /z in diameter. Four of the spores 

 are shown more magnified in Plate 3, fig. 18. A slightly wavy 

 appearance is produced by the shadows of overlying somatic 

 cells. 



Specimen 14. — Plate 6, fig. 46. This is an immature coeno- 

 bium containing thirty-two oogonidia of about 37 p in diameter 

 and an antheridium consisting of a sperm platelet. This sperm 

 platelet is a little above and to the left of the center of the 

 picture. The platelet consists of sperms, but whether the group 

 is still complete, and whether nearer to sixty-four or to one hun- 

 dred twenty-eight, I am unable to make out. On the opposite 

 side of the coenobium there is an empty antheridial site that 

 is symmetrically located with reference to the antheridium. 5 Be- 

 low the middle of the coenobium and halfway to the left there 

 is another vacancy like an antheridial site. 



Specimen 15. — Plate 6, fig. 47. This is the most mature of all 

 the female coenobia figured. Like all the other coenobia of this 

 series it is very much compressed under the cover glass, having 

 a thickness of only about 56 p. It measures 545 by 650 p, being 

 longer and broader than when the picture was taken. It then 

 measured 515 by 620 p, and its dimensions before compression 

 were probably nearer 500 by 600 p. The spacing of the so- 

 matic cells ranges from about 23 ^ forward to about 10 p at 

 the back. Taking 570 /* as a mean diameter and 14 p as the 

 average spacing of the cells, we get 6,000 as the number of cells. 

 This may be too high on account of the flattened condition of 



'This was overlooked until the preparation was studied from the back 

 by the use of a Zeiss achromatic objective B (12 millimeters equivalent 

 focus) . 



