lo NATURAL SCIENCE. Jan., 



were stopped, the rhythm was found to persist for a sliort time, the 

 shoot or stalk actuaUy curving in opposition to gravity for the half- 

 hourly interval before finally obeying the impulse to grow downwards. 



A similar effect was observed with heliotropic curvatures, for 

 which seedlings of canary grass were used, the rotation being, of 

 course, in a horizontal plane. 



In one case, after the clock was stopped, the seedlings curved 

 away from the light, for two half-hourly intervals, separated by one of 

 curvature towards the light, so strongly were they imbued with the 

 artificially-induced rhythm. The authors were evidently much struck 

 with the result of their experiment ; " to watch the movement of the 

 free end of the shoot," they say, " and to see it reversed exactly at 

 the expiration of half an hour is an experience so impressive as to 

 compel belief. When a shoot is in a thoroughly rhythmic state, it is 

 possible to prophesy to a minute at what time the reversal will take 

 place." They compare the persistence of the rhythm after cessation 

 of the stimulus to habit, like that acquired by a man who, after being 

 regularly called for a time at 6 a.m. will awaken of his own accord 

 at that hour. In the case, however, of the man, something in his 

 surroundings, such as duration of light, may unconsciously affect 

 him, but in the above experiments with plants, no such factor can 

 have intervened, and the rhythm must be the result of an "internal 

 chronometry," associated probably with the course of nutrition. 



Recent Progress in the Study of Alg^. 



The subject of the diseases of seaweeds is beginning to attract 

 attention. So far, all that is known relates to the familiar Vaucheria 

 galls and to the occurrence of Chytridieae in Sphacelaria, Cladostephus, 

 Ceramium, &c., as recorded by Magnus in the German North Sea 

 Commission's Reports ; while there are two papers by Miss Barton, 

 one on galls in Rhodymenia caused by a copepod [Jouvn. Botany), and 

 another on the malformations of Ascophyllum and Desmarestia [Phyco- 

 logical Memoirs). The thread-worm (Tylenchus fucicola), which causes 

 the malformation of Ascophyllum, has been minutely described and 

 beautifully figured by Dr. de Man in the recently issued Festschrift in 

 honour of Professor Leuckart. Dr. Schmitz has described, at the 

 British Association, Edinburgh, and in the Botanische Zeitnng, certain 

 tubercles of Florideae, caused by the inevitable Bacteria ; and a 

 further contribution of great interest will shortly be made to the 

 subject by Miss Frances Whitting, who is studying remarkable mal- 

 formations of Sarcophycus, a Fucaceous Alga of the southern seas. 

 This note of the literature of the subject may serve to call further 

 attention to a very promising field of study. 



A very admirable example of true methods in the study of 

 Cryptogamic Botany is to be found in a memoir on the Algae of 

 P. K. A. Schousboe, contributed by M. Ed. Bornet to the Societe 



