MYXOMYCETES. SLIME MOLDS ioi 



the nuclei may be distinct (Fig. 21, a). The number of amoeba? is 

 increased by division, probably by a kind of budding process. Starch 

 is present in the host cells but the amoeba gives only a reaction for 

 oil. No migration of the amoeboidal stage from cell to cell has 

 been observed. Several nuclei are present in each amoeba, and as 

 the number of the latter is increased they become rounded and 

 pressed closely together into what is practically a plasmodium. 

 The spore-forming stage is then initiated, accompanied first by 

 peculiarities in the nuclei, which seem to disappear more or less, 

 according to Nawaschin ; and this stage is followed, upon again 

 clearly distinguishing the nuclei, by a new form of nuclear divi- 

 sion, mitotic and simultaneous in all nuclei (Fig. 21, b and c). 

 There may be successive simultaneous divisions, and then the spores 

 are differentiated by the formation of a cell wall around each nucleus 

 and surrounding cytoplasm. Two stages in the differentiation of 

 the spores are shown in Fig. 21, d and e. 



Olive x and Jahn 2 have recently described what seems to be a 

 sexual process in certain Myxomycetes (notably in Ceratiomyxa). 

 It remains to be seen how these observations will finally be inter- 

 preted, and further, if there may also be fusion of the nuclei in 

 the case of Plasmodiophora. In this connection it may be stated, 

 however, that some mycologists doubt the relationship of Plasmo- 

 diophora with the Myxomycetes. 



At maturity most of the pathological cells are packed full of 

 the spherical thick-walled spores, and the latter are perhaps set 

 free only by the disintegration of the roots. Certain unusual 

 appearances, moreover, have been described, but these are not 

 understood. In from four to twenty-four hours the spores will 

 germinate in water in which some of the host tissue has been 

 teased out, the contents of each spore escaping in the form of an 

 irregular protoplasmic mass which may quickly change its form. 

 There is at first, for the most part, an appearance of an elongated 

 process or cilium, which doubtless permits rapid motility, denoting 

 also a swarmspore stage. In the swarmspore stage a nucleus and 



1 Olive, E. W. Cytological Studies on Ceratiomyxa. Trans. Wis. Acad. Sci., 

 Arts and Letters 15 (2) : 753-774- 1907. 



2 Jahn, E. Myxomycetenstudien, VI Kernverschmelzungen. . . . Ber. d. Deut. 

 Bot. Ges. 25 : 23-26. 1907. 



