ZOOLOaY AND BOTANY, ■ MIOEOSCOPY, ETO. 435 



firms De Bary's view that the increase in diameter of the internocles of 

 palm-stems is due to the increase in volume of the elements already in 

 existence, rather than to any fresh formation of cambium. Prof. Eichler 

 found this increase to be on the average not less than that of the stems of 

 Dicotyledons and Conifers. The capacity for this increase in size on the 

 part of the elements may be retained for a very long period. 



Growth of Pollen-grains.* — By observation of the proportion between 

 the amount of carbon dioxide evolved, and that of oxygen absorbed, M. L. 

 Mangin finds that the growth of pollen-grains is effected in three different 

 ways. In the case of grains containing abundance of starch, such as those 

 of Betula verrucosa, Iris pseudacorus, Plantago major, the hazel, hornbeam, 

 poppy, &c., their germination is independent of the nutritive substratum, 

 they consume their own reserve-material, and the production of carbon 

 dioxide remains constant. In grains containing no starch, such as those of 

 AgrapMs nutans, Narcissus pseudo-narcissus, Gentiana lutea. Digitalis, Vinca, 

 &c., they obtain their food-material from the outside, and then disengage a 

 large amount of carbon dioxide. In some ConifersB and in NympJisea alba, 

 the reserve of starch in the pollen-grains does not disappear, but fresh 

 supplies are formed in the cavity of the pollen-grain and in the pollen-tube, 

 which are used up by the latter in its developement. M. Mangin's observa- 

 tions were made on pollen-grains made to germinate artificially in a nutritive 

 medium, such as glycerin or a solution of sugar. 



Ripening of Seeds.j — M. A. Muntz states that unripe rye-grain con- 

 tains a notable proportion of synanthrose, a sugar analogous to cane-sugar, 

 and only found up to the present time in the roots or tubercles of certain 

 Compositee. The proportion in the dry grain varied between 45 per cent. 

 and 6*85 per cent. Young colza seed contains cane-sugar and a reducing 

 sugar having the rotatory power of invert-sugar ; at maturity cane-sugar 

 alone remains. By determining from time to time the sugar, starch, oil, and 

 nitrogenous matter in a constant number of colza seeds, the author finds 

 that the glucose diminishes gradually and disappears, the cane-sugar 

 increases, the starch, always present in small quantity, gradually diminishes, 

 the nitrogenous and oily matters constantly increase. It therefore appears 

 that the seed itself does not contain the carbohydrates which undergo 

 transformation into oil ; but that sugar and starch constantly flow there, 

 and disappear after a short sojourn, thus probably furnishing the material 

 out of which the oil of the seed is elaborated. 



(3) Movement. 



Ascent of Sap.| — According to Prof. S. Schwendener, the most recent 

 investigations of the movements of water in plants tend more and more to 

 show the insufficiency of the imbibition theory, and to lead to the conclu- 

 sion that the seat of these currents is mainly the cavities of the tracheids 

 and vessels rather than their walls. A fresh series of experiments and 

 observations undertaken by him confirm these results. During the summer 

 months the stems of most lofty trees contain no unbroken columns of 

 water. The suction from the leaves and the root-pressure are not by 

 themselves adequate to account for the rise of the sap ; other factors 

 must be sought for ; these are not yet fully known ; but among the more 



* Bull. Soc. Bot. France, viii. (1886) pp. 512-7. Cf. this Journal, ante, p. 269. 



t Ann. Agronom., xii. (1886) pp. 399-400. See Journ. Chem. Soc. Loud., 1887, 

 Abstr. , p. 173. 



J SB. K. Preuss. Akad. Wiss. Berlin, 1886, pp. 561-602 (3 flgs.). Cf. this Journal, 

 1886, p. 1016. 



