[Vol. XLVII 



romosomes 

 econd, the 



284 THE AMERICAN NATURALIST [Vol. XLVII 



sporophyte cell with the diploid number of ch: 

 can grow directly into the gametophyte ; second, 

 gametophyte can arise from the spores in the usual man- 

 ner, except that the reduction division is discontinued. 

 Examples are known for both cases. After discussing 

 the cell division of the more interesting cases of somatic 

 parthenogenesis, he sums up the families in which it 

 occurs, as follows : 



1. Polypodiacea? {Athyrium Filix-fcemina var. claris- 

 sima Bolton and var. unco-glow cral urn Stansfield; Scolo- 

 pendrium vulgar e var. crispum Drummondce). 



2. Marsiliaceas (Marsilia Drummondii R. Br.). 



3. Ranunculaceae (ThaUctrum purpurascens, Th. 

 Fendleri). 



4. Rosacea? (Alchi milln § Eualchimilla). 



5. Thymeheaceai (Wikstroemia indica). 



6. Composite (Antetmaria alpina, A. fallax, A. neo- 

 dioica; Taraxacum; Hieracium § Archier actum and 

 %Pilosella, almost completely). 



According to Juel (1900, 1904), Murbeck (1901), Guerin 

 (1904) and. Strasburger (1904, 1907), somatic partheno- 

 genesis is simply a vegetative process, the egg being 

 merely an ovate-shaped body cell of the sporophyte. 

 Winkler disagrees with this opinion, for if it be true, the 

 female individuals of parthenogenetic plants could pro- 

 duce only female offspring. But this is not the case, for 

 from parthenogenetic seed of ThaUctrum Fendleri, Day 

 obtained seeds which yielded abundantly staminate and 

 pistillate plants. Thus, it is conclusively proven that 

 cells are not always equivalent, even though they are 

 physiologically and morphologically alike. 



Two theoretical cases of generative parthenogenesis 

 are given as thinkable ; first, the whole cycle of develop- 

 ment could occur without a change in the number of chro- 

 mosomes, that is, the haploid number is retained through- 

 out ; second, a regenerative doubling of the chromosomes 

 could appear in the development of an egg with the hap- 

 loid number into the sporophyte. No examples of the 

 latter are known to occur in the plant kingdom. 



