Morphologie etc. — Varietäten etc. — Physiologie. 41 



York, H, H., The origin and development ofthe embryo- 

 sacand embryoof Dendrophthora opuntioides and Z). gracile. 

 ßotan. Gaz. LVI. p. 89-111, 200—216. pl. 5-7. 1913.) 



Like certain other members of Loranthaceae the genus Den- 

 drophthora presents the puzzling structure known as the "mamelon". 

 The present study goes to show that Treub correctly interpreted 

 this as an elongation of the floral axis which in this case produces 

 two simplified ovules. These usually consist of practically naked 

 nucelli, but may show vestiges of integuments. In development of 

 the megaspores of D opuntioides no chromosome reduction seems 

 to occur, although there is a synaptic stage; two cells are formed, 

 and the one in the chalazal portion gives rise to an embryosac, 

 which grows downward in the mamelon, outward, then upward 

 into the tissue of a carpel, thus assuming a hook shape with the 

 shorter end of the hook lying in the mamelon. Finally the proximal 

 ends of the two sacs fuse with one another. Seven or eight nuclei 

 are found in each sac, and they appear to be formed amitotically. 

 Two of these are antipodals, two are polar nuclei, and three or 

 four make up the Qgg apparatus. Other irregularities occur in the 

 relation of these nuclei. Pollination does not occur, but an embryo 

 develops in one of the two sacs thus: the egg nucleus gives rise to 

 a mass of tissue, a central cell of this produces the embr^^o, while 

 the remaining cells give rise to the endosperm. This mode of for- 

 mation of an embryo i^ compared with what Farmer and Digby 

 have called "pseudo-apogamy" in ferns. Comparisons are instituted 

 between this genus and other parasitic genera of this and other 

 families. M. A. Chrysler. 



Heetor, P. G,, Notes on Pollination and Cross-ferti- 

 lisation in the common Rice plant, Orysa sativa, 

 Linn. (Mem. Dept. Agr. Bot. Ser. VI. 1. p. 1 — 10. 1913.) 



From two years' experiments at Dacca on a large number of 

 varieties of rice cultivated in Lower Bengal the author draws the 

 following conclusions: 



1) In Lower Bengal cross-fertilisation may take place to the 

 extent of about 4 percent. 



2) This cross-fertilisation takes place wholly through the agency 

 of the wind and would seem to be effective only between flowers 

 of adjacent plants to a radius of a few feet. 



3) Segregation along Mendelian lines appears to take place 

 e. g. in grain colour. 



4) To avoid risk of contamination from cross-fertilisation seed 

 of varieties must be kept free from accidental mixtures. 



W. G. Craib (Kew). 



Jost, L., Vorlesungen überPflanzenphvsiologie,3. Aufl. 

 (XVI. 760 pp., 194 Textb. Jena, G. Fischer 1913.) 



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