700 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



used on the quarter-hourly period, the authors write : " This experiment is 

 remarkable as showing that the plant may acquire a rhythm in a very 

 short time, e.g. after four periods of a quarter of an hour each." In the 

 case of the Oak seedling, used for the half-hourly period, the authors 

 explain that " We give this experiment in order to make it clear that 

 there is no necessary connection between the heliotropism and the quarter- 

 hourly period, and that a plant can acquire a half-hourly rhythm by 

 alternating stimuli." Needless it is to say that all the experiments are 

 of great interest, and in detail which cannot here be referred to. From under 

 the head of "General Remarks" we may take the following paragraph : 

 " All we can do is to compare our results with other periodic phenomena. 

 For instance, when the stimulus is given by the alternation of day and 

 night, we get the diurnal periodicity of sleeping plants, which, as in our 

 experiments, continues after the stimulus has ceased. It seems to us that 

 such natural rhythms, as w T ell as our artificial phenomena, are intelligible 

 only as modifications of a fundamental rhythmic faculty in plants. Such a 

 faculty exists as circumnutation, and we may point out that the possibility 

 of regulating artificially the rhythmic growth of a plant is in entire 

 agreement with the fundamental idea of ' The Power of Movement in 

 Plants,' namely that growth-curvatures are modifications of circumnuta- 

 tion."— B. I. L. 



Riella, Development in the Genus. By Morten P. Porsild {Flora, 



vol. xcii., 1903, pp. 431-456 ; 8 cuts. — The starting-point of this work was 

 the raising of a sp. B. Paulsenii in a sample of dried mud from the banks 

 of a brackish pond in Bokhara brought back by the Danish Pamir 

 Expedition. Several other species were studied. The early stages of 

 germination take place well on wet filter-paper, but the plants here soon 

 become abnormal ; for continuous growth kaolin is the best substratum. 

 The product is an erect multicellular "primordial lobe" (better " proto- 

 thallus "), a flattened oval plate, on a narrow stem supported by numerous 

 rhizoids. The upper part is of adult (" ausgewachsen ") cells, and it is 

 from the lower merismatic part that the stem proper arises ; on its margin 

 a vegetative point arises pushing aside the " lateral lobe," and forming 

 on one side the stem and leaves, on the other the dorsal wing with the 

 sexual organs, or two may arise symmetrically. A distinct apical cell is 

 only formed later, and not at all in etiolated or weak plants ; it lies 

 between wing and stem, its segments going alternately to one and the 

 other. The formation of reproductive organs may be very precocious. 

 Gemnne may arise from the margins of the plants ; they are oval plates, 

 with a pair of deep notches nearer to one end ; the merismatic tissue 

 from which the growing-point arises lies at the base of the larger lobe 

 near the notch. — AI. H. 



Roadside Plantations, Contributions to the Study of. By N. 



Beveri {Ball. B. Soc. Tosc. Ort. 11, p. 315 ; November 1903).— The 

 paper has more particular reference to the plantations in the city of 

 Rome. The author first mentions the conditions which are unfavourable 

 to tlic normal growth of such trees ; these are deficient composition of the 

 soil due to the accumulation of building refuse ; the presence of sub- 



