60 



PRINCIPLES OP PLANT-TERATOLOGY. 



Leitgeb, whose paper is not at present accessible to 

 the writer, ascribes the phenomena of " double " 

 sporogonia to the fact that the growing point of the 

 developing sporogonium had become injured by some 

 external agency such as frost, as a result of which 

 lateral cells assumed its role. 



Gyorrfy gives the following brief summary of the 

 views held on the origin of " double " sporogonia of 

 Bryophytes, which are amplified here and there by 

 remarks within brackets : — 



1. Entry of two antherozoids into one archegonium 



Fig. 17. Bryum saxonum. Apex of capsule showing three tiers of peristome 

 teeth. (After Monkemeyer.) 



[giving rise to formation of two capsule's and subse- 

 quent fusion of their setae]. 



2. Development of two egg-cells in one arche- 

 gonium (Brongniart) [Hofeneder] (Le Dien). 



3. Fusion of two sporogonial embryos belonging to 

 two different archegonia (Schimper, Bescherelle). 



4. From one egg-cell (Pfeffer, Leitgeb [Gyorrfy] 

 [Monkemeyer in Bryum argent eum~\). 



In connection with the second and fourth theories 

 it may be mentioned that two egg-cells in a single 

 archegonium have been described by Coker in Milium, 

 by Bliss in Polytrichum juniperinum, and by Hofeneder 

 in Bryum caespiticium. 



