938 SUMMARY OF CURRENT RESEARCHES RELATING TO 



however, consider that this is due to the direct influence of light, but 

 only indirectly, in the same way as Famintzin has shown in the case 

 of Spirogyra. 



Influence of Gravitation on the Movements of Chlamydomonas 

 and Euglena.* — F, Schwarz has tried a series of experiments on 

 this subject, from which he concludes that gravitation is the deter- 

 mining cause of the direction of the movements of Euglena and 

 Chlamydomonas in the dark under certain conditions. This may 

 take place in two ways : — Firstly, gravitation may act in the same way 

 as light — as a stimulant, i.e. these organisms may be sensitive towards 

 gravity in the same way as they are towards light ; gravitation brings 

 forces into play which place their longer axis in a certain direction, 

 in which direction movement then takes place. Secondly, the objects 

 may place themselves, in consequence of the excentric position of 

 their centre of gravity, in the resting position, so that the anterior 

 colourless end is turned upwards; gravitation would in this case 

 cause an upward motion without acting as a stimulant. 



If the calling forth by gravitation of phenomena of movement and 

 growth is called geotropism, these movements may be regarded as 

 geotropic ; but the author proposes for this special phenomenon the 

 term geotaxis, corresponding to the similar phenomenon of phototaxis 

 produced by light. 



Chytridiacese.t — E. Fisch has observed three new forms of 

 Chytridiaceae growing on green water-plants, one of them the type of 

 a new genus. 



The new genus (Beesia) is distinguished from all other genera of 

 the order by the possession of zygospores, and is thus characterized : 

 — Vegetative structure amoeboid ; reproduction by zoosporangia, with 

 long neck projecting into the watei*, and uniciliated zoospores, which 

 conjugate in pairs and produce resting-spores ; these, on germinating, 

 give birth to zygospores, which penetrate singly into the host. In 

 addition to these zoospores are others not differentiated sexually 

 which produce these reproductive organs directly. B. amoeboides 

 lives in the cells of Lemma. 



The genus Chytridium he thus defines : — Zoosporangia of various 

 forms and opening in various ways ; zoospores not conjugating ; in the 

 summer producing again zoosporangia, in the autumn resting-spores ; 

 the latter, on germination, again producing non-conjugating zoospores. 



Bhizidium has zoosporangia and resting-spores formed from a 

 strongly developed much-branched cell or mycelium ; zoospores not 

 conjugating; secondary zoosporangia and resting-spores often pro- 

 duced in intercalary and terminal positions. 



Fisch regards Beesia as the lowest form of the Chytridiacese, 

 which he considers as related to the Ustilaginese, through Protom,yces 

 as a connecting form, rather than with the Peronosporese. 



* Ber. Deutsch. Bot. Gesell., ii. (1884) pp. 51-72. 



t Fisch, K., 'Beitriige zur Kenntuiss der Chytridiaceen.' Erlangen, 1884. 

 See Bot. Centralbl., xviii. (1884) p. 225. 



