to NATURAL SCIENCE. JAN., 
were stopped, the rhythm was found to persist for a short time, the 
shoot or stalk actually 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, 1n 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&. 
Tue 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 Chytridiez in Sphacelavia, Cladostephus, 
Cevamium, &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 (Fourvn. 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 Zeitung, certain 
tubercles of Floridew, 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 Savcophycus, 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 Algz of 
P. K. A. Schousboe, contributed by M. Ed. Bornet to the Société 
