314 Myxophycece 



but Borzi 1 has observed the formation of some rather remarkable 

 spores in the genus Anabcena. A single vegetative cell divides 

 into two distinct portions which subsequently coalesce, the product 

 having the characters of a nascent spore. 



Many of the Myxophyceae exhibit considerable polymorphism, 

 passing through a number of diverse states at different periods of 

 their life-history. Much confusion has arisen with regard to this 

 polymorphism and many extraordinary statements have in conse- 

 quence been made concerning the unicellular forms of the blue- 

 green Algae. Itzigsohn, Hansgirg and Wolle have all regarded the 

 plants of the Chroococcaceae as stages in the development of the 

 more highly organised blue-green Algse, and the last-mentioned 

 author has gone so far as to state that " it is now clearly evident 

 that all these so-called unicellular plants constitute nothing more 

 or less than conditions in the plant-life of higher forms 2 ." I have 

 previously pointed out the absurdity of this statement 3 , which is 

 erroneously based upon one. of the best known facts concerning the 

 Myxophyceae, namely, the ability of many of the lower forms of 

 blue-green Algae to live only under the same conditions of environ- 

 ment as the higher forms with which they are so frequently 

 intermingled. There is no direct evidence in proof of the generic 

 or specific identity of many of these forms which live intermingled 

 in a common gelatinous matrix, and there is rarely much difficulty 

 in discriminating between the more or less unicellular stages of 

 the higher types and the unicellular or colonial plants of a lower 

 type. 



Some of the Myxophyceae, principally of the genera Scytonema, 

 Stigonema and Nostoc, are regularly found in symbiotic relation- 

 ship with Fungi to form the dual organisms known as Lichens. 

 The Algae which have thus lost their individuality become con- 

 siderably modified and generally lose almost all traces of their 

 original specific characters. 



A few blue-green Algae belonging to the Oscillatoriaceae exhibit 

 spontaneous movements, generally of a slow, oscillating, gliding, or 

 rotatory character, and concerning which no convincing explana- 

 tion has yet been offered. It is in the genus Oscillatoria that 



1 Borzi in Bull. Soc. Bot. Ital. 1895, p. 208. 



2 Wolle, Freshw. Alg. U.S. p. 330. Plates clxxxiv and cxci in Wolle's text- 

 book are typical examples of the crude drawings of the Myxophyceee given by that 

 author. 



3 G. S. West in Journ. Bot. Febr. 1899, pp. 52, 53. 



