APPENDIX 625 



As the mycorrhiza invades the cells of the young tissue, their con- 

 tents are mostly destroyed, except the nucleus, which remains intact. 

 In the earlier stages the hyphai are nearly uniform in thickness, but 

 later they undergo a sort of degenerative process, forming vesicular 

 thin-walled masses, which seem to be finally destroyed by the action 

 of the prothallium cells. ''Symbiosis" thus would seem to be a case 

 of mutual parasitism, the fungus l)eing active in the earlier stages, but 

 later being destroyed by the activities of the host-cells. 



P. 236. The sex-organs in both O. Moluccanwn and O. pendulum 

 arise in acropetal succession, the youngest ones being close to the 

 apex of the branch. There is no definite relation of antheridia and 

 archegonia, the two being irregularly intermingled. 



P. 237. For details of the development of the antheridium, see 

 Campbell (29, ^t,). 



P. 237. The spermatozoids are probably the largest known among 

 the Pteridophytes. Those of O. pendulum are larger than those of 

 O. Moluccanum, but the nuclear portion is less elongated. 



Just before the final division of the sperm-cells, the nucleus shows a 

 small but distinct nucleolus, and in favorable preparations two small 

 rounded bodies, the blepharoplasts, can be distinguished. The 

 chromosomes are very numerous, but the number could not be deter- 

 mined. 



After the final mitosis is completed, the nucleus shows a coarse 

 reticulum, but no nucleolus can be seen. Before any evident change 

 occurs in this nucleus, the blepharoplast becomes elongated, and forms 

 a delicate thread which stains strongly with gentian-violet. 



The nucleus next elongates slightly, and the reticulate appearance 

 becomes very conspicuous. In the reticulum are large strongly 

 staining chromatin masses, which apparently arise from the coalescence 

 of several chromosomes. The nucleus now becomes indented on one 

 side and in profile appears crescent shaped. As it elongates it assumes 

 the form of a curved thickened band, tapering at the forward end, 

 which is sharply pointed. The chromatin masses become more and 

 more coalescent, until finally the elongated curved nucleus appears 

 almost perfectly homogeneous. 



The blepharoplast now becomes a spiral band, which connects with 

 the nucleus, and with it forms the body of the spermatozoid. The 

 central part of the cell contents is enclosed in the coil of the spermato- 

 zoid, and probably, as in other Ferns, forms a vesicle attached to the 

 free-swimming spermatozoid. 



The cilia begin to appear as short outgrowths of the blepharoplast, 

 40 



