292 Morphologie etc. — Varietäten etc. — Physiologie. 



4) Recouvretnent de l'ovule (teguments, nucelle). 

 Ici, Warming distingue les cinq types suivante , regardant la 

 nucelle comme un megasporange: 



a. L'ovule gymnosperme (eusporangiate monochlamyd^), 



b. L'ovule eusporangiate monochlamyde avec un tegument le 

 plus souvent epais et un gros nucelle, 



c. L'ovule eusporangiate dichlamyde avec deux teguments le 

 plus souvent minces et nucelle epais, 



d. L'ovule leptosporangiate monochlamyde ayant un seul tegu- 

 ment epais et un nucelle tres mince, 



e. L'ovule leptosporangiate dichlamyde avec deux teguments 

 minces et nucelle mince. 



Le type leptosporangiate est considere comme derive du type 

 eusporangiate. Quant aux teguments il existe vraisemblabiement des 

 Angiospermes qui n'ont jamais eu plus d'un tegument. D'ailleurs un 

 seul tegument peut se produire de deux soit parl'avortement du tegu- 

 ment externe ou interne soit par fusion des deux. Le dernier cas 

 se trouve p. ex. chez les Renonculacees, oü ce sont principalement 

 les genres ä ovaire pluriovule qui ont deux teguments libres ou 

 partiellement reunis tandis que les ovaires uniovules ont un tegu- 

 ment unique. 



Le travail contient des observations sur la structure de l'ovule 

 dans les groupes suivants: Primulales, Plombaginacets, Diospyrales, 

 Cucurbitacees, Rosales, Umbellales, Cornales (comprenant ri//^/)«?'75 



Ove Paulsen (Copenhague). 



Gates, R. R., Recent Papers on Oenothera Mutations. (New 

 Phyt. XII. p. 290—302. 1913.) 



The author discusses and criticises the more recent work upon 

 I) the heredity and Variation, 2j the cytology, and 3) the systema- 

 tics of the Oenothera^. A bibliography is included giving the titles 

 of thirty papers on these subjects all of which have been published 

 within the last six years. The author concludes that the Mendelian 

 theory of mutation has been disproved and the premutation theory 

 of De Vries rendered unnecessary by the study of the nuclei. He 

 considers that the main achievement of the last three years has 

 been to show that mutation is an independent process requiring a 

 special explanation. Agnes Arber (Cambridge). 



Böse, J.C., On Diurnal Variation ofMotoexcitability in 

 Mimosa. (Ann. Bot. XXVII. p. 759-779. 17 figs. 1913.) 



The author describes experimental methods by which the moto- 

 excitabiliiy of Mimosa is tested, every hour of day and night, b)- 

 the amplilude of the response to a Stimulus; this is effected by means 

 of automatic devices which excite the plant periodically b}^ an ab- 

 solutely constant Stimulus and record the corresponding mechanical 

 response. From the results obtained, it is found that the excitability 

 undergoes a Variation which is characteristically different at different 

 times of the day. In a typical case, the excitability reached its 

 maximum value at 1 p. m.; there was then a continuous fall in 

 excitability, the minimum being reached at 9 a. m. next day, when 

 the plant was practically insensitive; the excitability was then gra- 

 dually enhanced in a staircase manner tili it again reached a maxi- 

 mum at 1 p. ra. The effect of sudden darkness was to induce a 



