298 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Tuberculisation of the Potato.* — N. Bernard applies his law that 

 the formation of tubercles on roots or underground stolons is the result 

 of the attacks of an endophytic fungus to the case of the potato. The 

 cause here is the well-known fungus Fusarium Solani, so frequently- 

 found as a saprophyte in decaying tubers. It does not, however, attack 

 the parenchynie of healthy tubers, but infests only the external suberous 

 layers of dead cells filled with air, in which the author always finds 

 the mycele and spores of this fungus. Experiments on the production 

 of tubers by sterilised and non-sterilised potato-plants confirmed this 

 conclusion ; and it obtains further support from the fact, that when the 

 potato was first intoduced into Europe, potato-plants grown from seed 

 frequently failed to produce tubers. 



Anatomy of Phoenix dactylifera and Chamaerops humilis.j — G. B. 

 Petrucci describes in great detail the anatomical structure of these two 

 palms, and argues against the prevalent opinion that they hybridise with 

 one another. The alleged Microphcenix decipiens, which has been de- 

 scribed as a hybrid between them, he regards simply as a variety of 

 Chamaerops humilis, a species which is very polymorphic, especially in its 

 fruit. 



£. Physiology. 



(1) Reproduction and Embryology. 



Polyembryony.j — A. Ernst thus classifies the modes in which more 

 than one embryo may be produced in Angiosperms. 



A. Pseudo-polyembryony : — 



1. Coalescence of ovules (Pyrus Mains, Loranthus europaeus, 



Viscum album). 



2. Division of the nucellus (Moras albas, Orchis Morio, Gym- 



nadenia conopsea, Coffea arabica ("r 1 ) ). 



3. Development of several embryo-sacs in one nucellus (Cheir- 



anthus Cheiri, Bosa livida, Trifolium pratense, Taraxacum 

 officinale). 



B. True Polyembryony : — 



a. Embryos " extra-saccal," arising outside the cells of the 



embryo-sac. 



1. Development of adventitious embryos from nucellar cells 



(Funlcia ovata, Nothoscordon fragrans, Citrus aurantia, 

 Mangifera indica, Euonymus latifolius, E. americanus, 

 Coslcbogyne ilicifolia, Clusia alba, Opuntia vidgaris). 



2. Development of adventitious embryos from cells of the 



inner integument (Allium odorum). 



b. Embryos " intra-saccal," formed from elements of the 



embryo-sac. 



1. Normal existence of two oospheres (Santalum album, 



Sinninghia Lindleyana). 



2. Synergid-embryos (Glaucium luteum, Mimosa Denhartii, 



Schrankia uncinata, Lilium Martagon, Iris sibirica, 

 Vincetoxicum nigrum, V. medium, Allium odorum, Tar- 

 axacum officinale, Aconitum Napellus). 



9 Oompto8 Reudus, rxxxii. (1901) pp. 355-7. Cf. tliis Journal, ante, p. 55. 



t Malpighia, xiv. (1900) pp. 300-60 (4 pis.)- X Flora, lxxxviii. (1901) pp. 62-70. 



