602 SUMMARY OF CURRENT RESEARCHES RELATING TO 



duction of sperraatozoids, and in certain anatomical characters of the 

 reproductive and vegetative organs. Like the extinct Cycadofilices, it 

 possesses both Filicinean and Cycarlean characters ; but, while exhibiting 

 traces of the affinity of Cycads and Ferns, it represents, in all probability, 

 a very ancieut type which may have been merged in the Cordaitales in 

 the Palaeozoic era. 



Cypress-Knees.* — Mr. T. Meehan has come to the conclusion that 

 the so-called " knees " of Taxodium distichum, common in the swamps of 

 Florida, are not, as has been supposed, organs containing aeriferous 

 tissue which is useful to the plant ; but that they are simply excrescences 

 caused by the attacks of a fungus, the hollowness of the main trunk 

 and of the excrescences being due to the same cause. 



Root-nodules of Alnus and Elseagnus.f — Herr L. Hiltner states 

 that, like the Leguminosae, alders, when provided with root-nodules, grow 

 normally in the absence of combined nitrogen. But, unlike leguminous 

 plants, alders develope normally in water-cultures when the nodules 

 remain covered with water. Elseagnus, when inoculated with the root- 

 bacteria, will also grow normally without combined nitrogen. The 

 organism which produces the nodules, Franhia subtilis, appears to be 

 the same in all cases. The author regards it as a connecting link between 

 bacteria and fungi. 



j3. Physiology. 

 (1) Reproduction and Embryology. 



Impregnation in Dicotyledons. J — Pursuing his investigations on 

 this subject, Herr S. Nawaschin has devoted himself especially to two 

 widely separated families, the Ranunculacese and the Composite. The 

 general result has been a confirmation of his previous conclusion that 

 the fusion of the male with the female nucleus is a true process of im- 

 pregnation ; and whether this takes place in the ovum-cell (oosphere) or 

 in the endosperm-cell, the signification is the same. If (in the latter 

 case) no such fusion takes place, no endosperm is formed. 



In Delphinium elatum (Ranunculaceae) a material deviation from the 

 mode in Liliaceae was established in the fact that the two polar nuclei 

 fuse together before impregnation, and the ovum-nucleus passes through 

 a long period of repose after its fusion with the male nucleus. Before 

 impregnation the male generative cells were detected, not only within 

 the pollen-tube as vermiform structures, but also during their fusion 

 with the ovum-nucleus and the embryo-sac respectively in the form of a 

 dense chromatin-knot. 



In Heliavthus (Composite) also the two polar nuclei fuse together 

 long before impregnation. The pollen-tube empties its contents into 

 the side of the embryo-sac, between the two synergids. The two 

 spermatozoids free themselves from the coarse-grained contents of the 

 pollen-tube ; one of them forces itself into the side of the ovum-cell, the 

 other attaches itself closely to the embryo-sac nucleus. The sperma- 



* Proc. Acad. Nat. Sci. Philadelphia, 1900, pp. 349-51. 



t Forstl. naturw. Zeit., vii. (1898) pp. 415-23. See Journ. Chem. Soc, 1900, 

 Abstr. ii. p. 426. 



X Ber. Deutsch. Bot. Ges., xviii. (1900) pp. 224-30 (1 pi.) Cf. this Journal, ante, 

 p. 81. 



