100 ROMANCE OF LOW LIFE AMONGST PLANTS. 



which have been entangled together and rolled into a 

 ball, but of a plant growing in a dense mass, with the 

 filaments all of one kind, and disposed centrifugally 

 in one direction. At first the dense tuft may have 

 been attached to some matrix, at length becoming 

 free, and then by equal growth outwards obliterated 

 all trace of attachment, and assumed the spherical 

 form. Smaller and less solid tufts are conglobated 

 by other free-swimming algae, belonging to other 

 genera. 



What is Nostoc.'' 



Let us introduce this question by a quotation, which 

 gives, within a moderate compass, an explanation of 

 the problem. " Suppose, for instance, the student, 

 after a few hours' train, goes out into the open air, and 

 sees the gravel and short grass strewed with gelatinous 

 puckered olive-coloured masses, of which he perceived 

 no trace a few hours before, his curiosity is excited, 

 and he is anxious to ascertain the nature of this pro- 

 duction. Externally it presents no marked differences, 

 and within it seems to consist of a uniform jelly, 

 without anything to make him suppose that it can 

 be a mass of eggs. He examines it under the micro- 

 scope, and finds that it consists of necklace-like chains 

 of pellucid granules immersed in jelly of no definite 

 structure. Some of these are larger than the others. 

 He finds after a time that they change colour and 

 increase considerably in size, though still retaining a 

 regular outline ; presently, the matter contained in 

 their cavity becomes organized, and a new necklace of 

 spores is contained within it : in fact, he has a young 



