l6o ARCHEGONIATES. 



The processes incident to and accompanying fecundation in Zamia 

 differ only in minor details from those of Cycas. Certain phases of 

 these processes, however, as observed by Webber ('97, I, II, III), are 

 of special interest and importance. They are described as follows 

 ('97, II, p. 18): 



The proximal ends of the pollen tubes . . . which grow downward 

 through the apical tissue of the nucellus into a cavity formed in the prothallium 

 above the archegonium, have increased in length until the ends almost or quite 

 touch the neck cells of the archegonia, which protrude into the same cavity 

 (Fig. 65, A). It is interesting to note that the pollen tubes when they enter the 

 prothallium cavity, which is filled with air, do not grow at random, but bend 

 slightly outward and grow directly toward the archegonia. . . . The pro- 

 truding tip formed by the old pollen grain is plainly visible with a hand lens, 

 and is evidently the point which first comes into contact with the neck cells of 

 the archegonia. The neck cells are also distended and turgid, and are evi- 

 dently easily broken. If in this stage the end of a pollen tube be touched very 

 lightly with the flat side of a scalpel it bursts, and the antherozoids, together with 

 a drop of the watery contents of the pollen tube are quickly forced out, and the 

 pollen tube immediately shrivels up into a shapeless mass. . . . The pollen 

 tube evidently grows down until the end is forced against the neck cells, when 

 the tube bursts, discharging the mature antherozoids and the watery contents 

 of the tube which supplies a drop of fluid in which the antherozoids can swim. 

 . . . ('97, III, p. 226). 



As explained in my previous papers, several antherozoids commonly enter 

 each archegonium, two being usually found and sometimes three or four. The 

 entire antherozoid enters unchanged, swimming in between the ruptured neck 

 cells. Only one of the antherozoids is concerned in fecundation, and the others 

 are usually found between the protoplasm and the wall of the archegonium, 

 presenting their original form and appearance, or in some stage of disintegra- 

 tion (Fig. 66, A). Occasionally one of the antherozoids not concerned in fecun- 

 dation pushes for a short distance into the contents of the archegonium, as it is 

 always found in such cases to form a distinct body which stains very differently 

 . . . ('01, p. 65). That one which is utilized in fecundation swims into the 

 protoplasm of the archegonium for a short distance, where it comes to rest and 

 undergoes change. The nucleus slips out of its cytoplasmic sheath and passes 

 on alone from this point to the egg-nucleus, with which it unites. The spiral 

 ciliferous band remains at the apex of the egg-cell in the place where the nucleus 

 left. In very numerous instances, just after fecundation, it has been discovered 

 in this position, and there can be no douDt that this process is the one normally 

 occurring. It shows very plainly and presents nearly the original form of the 

 spermatozoid (Fig. 66, B), but is always stretched out much more than in the 

 normal spermatozoid. . . 



The method of escape of the nucleus from the body of the spermatozoid can 

 only be conjectured. It would seem, however, that the rapid boring of the 

 apical or spiral end into the egg-cell may cause too great a pressure on the 

 large body of the spermatozoid, resulting in its bursting and freeing the nucleus , 



