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THE AMEBIC AX NATURALIST [Vol. XLII 



cells in an archegonium with a poorly developed neck; it is 

 doubtful whether such eggs are capable of being fertilized. 



The sporophytic outgrowths on apogamous prothallia arise 

 coincident with the development of the cushion region. Super- 

 ficial cells on the underside increase in size, and from one of 

 these an apical cell is cut off which becomes the growing point 

 of a leaf. Meanwhile there is a rapid division of the neighbor- 

 ing cells in the interior so that an area of meristematic tissue 

 results which gives rise to the young sporophyte in direct con- 

 nection with the prothallial cells. A leaf and stem axis are 

 developed from two superficial apical cells, the root tip arises 

 endogenously. scalariform vessels appear in the tissue connecting 

 the developing leaf and stem, and finally there is differentiated 

 the young sporophyte with root, stem and leaf regions. Mitoses 

 are easily found in stages of this apogamously developed sporo- 

 phyte and always show 64 or 66 chromosomes, the gametophytic 

 number of the prothallium. Consequently, in Nephrodium 

 molle, there is no doubling of the number of chomosomes in the 

 development of apogamous sporophytes through nuclear migra- 

 tion and fusion as described by Farmer and Digby for the 

 polydactyla varieties of Lastrea pseudo-mas. It has not yet 

 been determined whether these apogamous sporophytes develop 

 spores. 



Apogamy in Nephrodium. therefore, presents conditions dif- 

 ferent from anything as yet recorded for plants, since following 

 normal sporogenesis a sporophyte is developed with the gameto- 

 phytic or haploid number of chromosomes fx), and there is no 

 place in the life history for the diploid or sporophytic number. 

 The case of Lastrea pseudo-mas var. cristata apospora is appar- 

 ently not the same since in that form apogamy follows apospory. 

 However it is possible that the apogamous sporophytes of 

 Nephrodium may be found at maturity to develop apospory and 

 thus swing into a type of life history similar to that recorded 

 by Farmer and Digby for the above form of Lastrea. The most 

 significant results of Yamanouehi's investigation is the clear 

 evidence that the morphology of the sporophyte does not de- 

 mand that its cells contain nuclei with the double or diploid 

 number of chromosomes (2x), in other words that the "number 

 of chromosomes is not the only factor which determines the 

 characters of the sporophyte and gametophyte, " a conclusion 

 indicated by the known cases in both ferns and seed plants 



