TIlRArSTOTllECA J 49 



Occasionally among the ordinary spores large irregular sjwre masses are 

 liberated. These masses slowly round up somewhat and encyst, sprout- 

 ing later without a swimming stage, (iemmae small, jjyriform or rarely 

 spherical, falling into spores in suitable environment. Oogonia borne 

 singly on short, straight, perpendicular stalks from the secondary hy- 

 phae, rarely from the primaries; 30-70;j. thick, spherical, smooth, and 

 very slightly pitted, the pits appearing only after staining with chlor- 

 zinciodide. Eggs i-io or rarely ii, usually 4-6 or 8, eccentric, with 

 a single large peripheral oil globule; size very constant, the diameter 

 about 18-22,1. Antheridial branches diclinous, arising from the sec- 

 ondary hyphae, very crooked, and quite stout; antheridia club-shaped, 

 cut off by a wall; antheridial tubes obvious. 



Rare. Found in such places as spring Ijelow Cobb Terrace, Arbore- 

 tum spring and branch, and in marsh on south edge of Glen Burnie 

 meadow. Known in America from Chapel Hill, N. C, and Great Bar- 

 rington, Mass. For other illustrations see Biisgen ('82), figs. 1-8; 

 .Minden ('12), fig. 7 on p. 556; and Weston ('18), pis. 4 and 5, and two 

 text figures. 



The actual fertilization of the egg has not been seen, but w^e have 

 observed the antheridia to become empty during the ripening of the 

 eggs. In no case was it found that an antheridium became attached 

 to an oogonium arising from the same hypha as itself, but occasionally 

 an antheridial branch may arise from the stalk of one oogonium and 

 extend to another from a different hypha, thus proving the plant not 

 to be dioecious. When the eggs first round up they show many oil 

 globules situated on one side (fig. 10). These globules are at first only 

 about 2,1 in diameter, but they gradually fuse until there are only two 

 or three larger ones from 851 to I5ix in diameter. Finally these globules 

 fuse into a single one, which is about i6;j. in diameter, and situated at 

 the periphery of the egg. The eggs are then ripe. In contaminated 

 cultures an oogonium will often sprout a new one, the old being emptied 

 into the new (fig. 9). This process may be repeated several times and 

 the eggs be formed finally in the terminal oogonium (fig. 8). Occa- 

 sionally two oogonia are produced upon one branch. 



After the encysting of the spores, the sporangial wall, which has 

 always been thin, breaks and begins to disappear, vanishing first as a 

 rule on one side near the end, and continuing to disintegrate until nothing 

 is left of it except a narrow circular ring at the base. This basal ring may 

 be cjuite conspicuous or almost entirely absent. Except in A. diibia this 

 method of dehiscence is entirely unique in water molds and is superficially 

 like that of the mold Mucor and its relatives. This resemblance was 

 remarked on at the time the plant was described, and Solms-Laubach 

 thought he saw another point of agreement between Mucor and our plant 

 in the upward bulging of the basal partition. The bulging is, however, 



