THEORETICAL CONCLUSIONS 415 



remaining four cells or nuclei are prothallial. According to this 

 view one synergid and the egg constitute the first archegonium, the 

 synergid being equivalent to the ventral canal cell; and the other 

 synergid and the upper polar nucleus constitute the second arche- 

 gonium. Neck cells are absent and both the archegonia are 

 fertilized, one giving rise to the embryo and the other to the endo- 

 sperm (Schurhoff, 1919, 1928). 



The third view, which may be considered first for convenience, 

 is based on the wholly erroneous assumption that one synergid is 

 sister to the egg and the second to the upper polar nucleus, and 

 that these two pairs of nuclei constitute two separate archegonia. 

 Langlet (1927) produced evidence to show that the synergids are 

 formed from one pair of sister nuclei and the egg and upper polar 

 nucleus from another pair. During recent years this has received 

 further confirmation and at present there is not a single authentic 

 instance where the contrary has been definitely established. 

 Schurhoff 's theory may, therefore, be rejected without further dis- 

 cussion. 



The second view, put forward by Porsch, has attracted consider- 

 able attention and is still favored by some embryologists (see 

 especially Nilsson, 1941; Schnarf, 1942). In support of it have 

 also been cited certain abnormal embryo sacs showing reversed 

 polarity. It is suggested thereby that both the archegonia, micro- 

 pylar as well as chalazal, were originally quite similar and that 

 either of them was capable of functioning in the ancestral type of 

 embryo sac (Swamy, 1946). 



There are, however, some serious difficulties in accepting Porsch's 

 view: 



1. It assumes that the female gametophyte comprises only two 

 archegonia, the prothallial tissue having disappeared completely. 

 Even if this could happen, it is surprising that the archegonia 



showing only two archegonia, each consisting of egg, ventral canal nucleus, and two 

 neck cells corresponding to synergids. This is regarded as essentially similar to 

 condition in Balanophora. F, as in E, but the two archegonia occupy opposite 

 poles of embryo sac; pollen tube enters chalazal end of embryo sac. G, as in F, 

 but pollen tube turns around embryo sac and enters it at micropylar end. H, 

 embryo sac, showing pollen tube entering directly from above, as in majority of 

 present-day angiosperms. /, embryo sac in which only upper archegonium is 

 functional and lower soon degenerates. (After Porsch, 1907.) 



