— 167 — 



bracht*. He depicts, moreover, a case of polyembryony in fig. 1 



and believes thai fig. 2 represents an earlier stage of this. It 

 should, however, be noted, that this adventive embryo „dicht an 

 dem Boden des Embryosacks entstanden ist'-, when generally the 

 adventive embryos encroach on the upper part of the ES. Stras- 

 bnrger (27) points out in his well known work on AlchemUla a 

 point which is of great importance in connection herewith: „Die 

 zur Anlage eines Embryosacks sich anschickenden Zellen . . . lassen 

 sich alsbald nicht mehr mit Sicherheit auf eine bestimmte Zellreihe 

 der Samenanlage zuriickfiihren. Ja manchmal mochte man. infolge 

 von Verschiebungen in der urspriinglichen Anordnung meinen, dass 

 sie ihren Ursprung aus einer Basalzelle der Anlage nahmen, was 

 jedoch recht nnwahrscheinlich ist und niemals unzweideutlich fest- 

 zustellen war'. As the archespor in AlchemUla is multicellular 

 and consequently not sharply defined against the chalaza-region, it 

 is of course difficult to decide such a matter. On the other hand 

 in Hieracium the archespor consists of but one cell, and conse- 

 quently there is no doubt as to the value of the aposporic embryo 

 sac Perhaps further investigations will show that the aforemen- 

 tioned cases in AlchemUla really should be considered as embryo 

 sac-, not embryo-origin. 



Treub (20) has described, in connection wilh the apogamy 

 in Elatostema, very peculiar seed formations. PI. 10 and 11 of his 

 work show, that in several cases two macrospores develop in the 

 same ovule. Some of his figures very much remind me of what 

 1 have found in Hieracium. I will, however, not pretend that 

 one of the two embryo sacs in his figures is of aposporic origin, 

 but a further cytological examination of this material will perhaps 

 show that both these „macrospores" are not always of the same 

 origin. In some cases Treub depicts tetrads which are quite 

 typical. However he cannot decide with certainty, if there is any 

 reduction of chromosomes. He says that: „il est peu probable 

 qu'elle ait lieu". Tetrad division without a reduction division is 

 not yet found or described, and consequently it seems to me that 

 another examination just from a cytological point of view is neces- 

 sary. It is not impossible that a tetrad with chromosome reduc- 

 tion is formed, and that the other, „macrospore\ is really a vege- 

 tative cell which develops like an embryo sac. 



Should it be proved that in the aforementioned species even 

 a vegetative cell can develop into an embryo sac as in Hieracium. 



