PYTIIIOPSIS 21 



lilizes the egg. Gemmae resembling sporangia or oogonia are present 

 in quantity, and after a rest form spores or germinate with tubes. 



Rather rare: occurring only eight times in our numerous collections, 

 as in brook behind Dr. Henderson's residence, February 29, 191 2 ; on south 

 side Glen Burnie meadow, March 18, 1912; in brook in Battle's Park, 

 March 25, 1912; in branch south of campus. May 13, 1912, etc. 



The species is sharply separated from P. cymosa by the much larger 

 and always smooth oogonia, larger eggs, larger sporangia, absence of 

 strictly basal antheridia and presence of elongated forms of sporangia. 

 Illustrations of the globular type of sporangia, which are the first to 

 appear in clean and vigorous cultures, are given in figures 3, 4, and 6. 

 They are of the same appearance as those of P. cymosa. The papilla 

 is usually formed at the tip when growth is acti^-e, but if there is a rest 

 it is as apt to be formed at any other point (figs. 4 and 6). Intermediate 

 and elongated forms are shown in figs. 5-10 and 13. As in P. cymosa 

 the internal pressure is dissipated before the last spores emerge and it 

 is often many minutes before all find the exit. As shown in the figures, 

 the papilla may be quite abrupt or may gradually taper into the body 

 of the sporangium. 



The oogonia are often closely associated with the sporangia (figs. 13 

 and 14), but the more common arrangement is a terminal oogonium 

 on a rather short lateral branch, as shown in fig. 2, with a single stalked 

 antheridium arising from immediately below it. The antheridial branch 

 almost invariably carries but a single antheridium, which is short, thick 

 and densely filled with protoplasm. The antheridial tube is quite con- 

 spicuous and its behavior is such that there is scarcely any doubt that 

 fertilization takes place. The protoplasm of the antheridium passes 

 into the tube and soon afterward no protoplasm or tube can be seen, 

 indicating the discharge of the former and collapse of the very thin- 

 walled tube. The tubes are distinctly shown in figs. 13-15- 



Oogonia with two eggs are not very rare. One of these with two 

 antheridia is shown in fig. 11. Oogonia with four eggs were seen twice. 

 One of these, of anomalous shape, is shown in fig. 16. The occurrence 

 of more than one egg in the oogonium of P. cymosa is quite rare. Hum- 

 phrey saw two eggs only once and our cultures of that species have not 

 produced any such oogonia. DeBary says that as many as three eggs 

 may occur in P. cymosa but their appearance is evidently of great rarity. 



