70 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Abnormal Nuclear Division.* — C. van Wisselingh has made a 

 detailed study of the various methods of abnormal division of the 

 nucleus to be found in Spirogyra when subjected to the action of 

 various reagents, chiefly dilute chloral-hydrate solution. His general 

 conclusion is that the various abnormal processes observed are not of a 

 special nature or of the nature of amitosis, but are to be considered as 

 processes of karyokinesis, though modified to a greater or less extent. 

 The evidence for amitosis in plants is reviewed, and its unsatisfactory 

 nature pointed out. Many of the observations are to be explained as 

 modifications of karyokinesis. The author has modified somewhat his 

 views on normal division ; he no longer believes that two of the six or 

 twelve chromosomes are derived from the nucleolus (or nucleoli), but 

 that a small portion only of the substance of these two special chromo- 

 somes is derived from the nucleolus. 



Spermatogenesis of Hybrid Peas.j — W. A. Cannon, continuing 

 his studies in plant hybrids, has investigated the nuclear development in 

 pollen-formation in hybrid peas, namely, Fillbasket X Debarbieux and 

 Express X Serpette. The hybrids investigated were of those of the 

 second generation, and they showed variation after the Mendelian law. 

 They matured their spores in exactly the same way as the pure ancestral 

 forms ; the first mitosis being heterotypic, the second homotypic. 

 The reduced number of chromosomes was seven, both in hybrids and 

 pure forms, the somatic number being fourteen. In the anaphase, how- 

 ever, of the last sporogenous division of both hybrids and of the pure 

 form, Fillbasket, the chromosomes were found associated in pairs ; this 

 condition is considered not to be the result of chance. It is clear that 

 abnormalities and irregularities of nuclear division (which have been 

 observed in some forms, probably in connection with their non-fertile 

 nature) do not form the basis for the variation of these hybrids. The 

 basis of variation is probably the same as that of variations in the pure 

 forms. 



Structure and Development. 



Veg-etative. 



Stem of Sicyos angulata.J — Fr. Tondera gives an account of the 

 morphology and the anatomy of the stem of this member of the order 

 Cucurbitaceae. The stem is a sympodial structure, and the arrangement 

 and course of the vascular bundles is clearly described and figured. 

 The five-angled stem contains a mass of collenchymatous tissue in each 

 of the angles, the well-developed parenchymatous ground-tissue is 

 bounded by a sclerenchymatous ring, and contains an inner and an 

 outer series of bicollateral bundles, the course of which through the 

 internodes is carefully followed. 



Saprophytic Gentianaceae.§ — -N. Svedelius describes some points 

 in the structure of species of Leiphamos and Voyria, from material 



* Bot. Zeit, xxxii. (1903) pp. 201-48 (3 pis.). 

 t Bull. Torrey Bot. Club, xxx. (1903) pp. 519-43. 



% SB. K. Akad. Wiss. Wien, Math.-naturwiss. CI. cxi. (1902) pp. 317-26 (2 pis.). 

 § Bihang. K. Svensk. Vet.-Akad. Handl., xxviii. (1902) Afd. iii. No. 4, pp. 1-16 

 (11 figs, in text). 



