88 SCIENCE PROGRESS. 



diameter which contain numerous nuclei, and between these 

 latter in some cases delicate walls are formed. As the 

 concentration of the culture-medium is increased the cells 

 keep on diminishing in length and approach the spherical 

 form, whilst the walls assume, with increasing frequency, 

 an oblique or even longitudinal direction instead of a trans- 

 verse one, this never happening under normal conditions. 

 We here meet, apparently, with fundamental disturbances 

 of growth ; the giant-cells are no longer capable of multi- 

 plication, but eventually die out. Other abnormalities will 

 not be referred to here, except to state that by cultivation 

 in I per cent, ammonium sulphate or lo percent, ammonium 

 chloride BasidiobohLs may be compelled to pass through a 

 " Palmella stage," which is unknown in the case of any 

 other mould. It isolates itself as spherical cells with thick 

 walls, and these free themselves from the old cell-envelope. 

 The interference with development is clearly more limited 

 in this instance than in that of the giant-cells above described. 



Similar results have been obtained in the case of some 

 alga^ ; in these, too, abnormalities may be produced by the 

 composition of the culture-medium, especially as regards its 

 concentration, though they do not go so far as in Basidio- 

 boliLS. Thus, Chodat and Huber founcP that in Pediastrtun 

 Boi'yamim the formation of daughter-colonies does not 

 occur in concentrated culture-media, and the cells some- 

 times become metamorphosed into large " hypnocysts " ; 

 Richter^has also seen abnormalities occur in other fresh- 

 water Algae when cultivated in salt solution. 



In passing on to the Phanerogams I would repeat, in 

 the first place, the words with which a distinguished in- 

 vestigator on the etiology of malformations, Peyritsch, opens 

 his treatise upon the origin of the formation of peloric flowers. 

 He says : " In studying the cause of the formation of peloric 

 flowers, and especially in reference to modifications of structure, 

 two points must be kept in mind. One refers localisation; 



^ "Recherches experimentelles sur le Pediastrum Boryanum" Bull. Soc. 

 bot. Suisse, 1895. 



^ Ueber die Anpassung der SUsswasseralgen an Kochsalzlosung," 

 Flora, p. ^ff., 1894. 



