338 



THE GUIDE TO NATURE. 



at a glance through the microscope, 

 distinguish it from a Conferva, or from 

 any of its more immediate kindred. 



While making a vain search for 

 those colorless and arborescent pro- 

 longations that, when present, act as 

 rootlets, I happily penetrated into a 

 secret, that for many evenings made 

 Ulothrix flaccida a charming guest at 

 the microscope table. At the lower- 

 most end of the thread-like filaments 

 which form these simple plants, and 

 near which the cells had become 

 brown, shrivelled and apparently dead, 

 nature was in the act of producing a 

 lichen. In one of the formative stages, 

 and an early one at that, here was a 

 lichen in process of development. Ti>at 

 grey and wrinkled object which we all 

 know by sight, and which seems to 

 ask for nothing but a sterile rock, or 

 a bit of dead bark in the sun, is not the 

 single, independent growth that it ap- 

 pears to be, but is a combination of 

 fungus and alga, a symbiosis in which 

 two distinct plants give and receive 

 a certain something, that to the one 

 is not necessary, but to the other is 

 essential, a result of this reciprocity 

 being that apparently half-dead thing, 

 which we so often reject as not worth 

 a moment's notice. Yet it is not half 

 dead ; it is doubly alive. 



It was upon the beginning of such 

 a combination that I happened, when 

 I found the green stain on the ground, 

 and brought bits of it away in the palm 

 of my hand. Here were filaments that 

 were neither Ulothrix complete, nor 

 Protococcns cells unaltered, for the lat- 

 ter were dividing 1 , chanenne: and de- 

 veloping on the ground where the rain 

 had washed them from the tree-trunk 

 above, and where the verdant patch 

 was increasing with every shower. 

 But some of the Protococcns cells had 

 been caught in the embrace of a color- 

 less thread (hypha) of a fungus, which 

 had divided itself so that it might at 

 once touch two surfaces of the cell, 

 while others had twined themselves 

 about the Ulothrix filaments, into sev- 

 eral of whose cells they had penetrat- 

 ed, and upon whose delicate spire they 

 were climbing. So young was the 

 combination, that, mingled with the 



growth, were fungous spores that were 

 just beginning to emit their colorless 

 threads, and were apparently reaching 

 out for the support and the nutriment 

 that only Ulothrix could afford. What 

 the lichen will become, the future alone 

 can tell. Nature may suppress it be- 

 fore it attains maturity, or some more 

 favored observer may solve the prob- 

 lem. 



This was my first meeting with 

 Ulotlirix ilaccida, but not the last. I 

 next observed it on the foundation 

 stones of my house. It appeared be- 

 tween the bricks in the garden walk ; 

 in a broad sheet on the surface of one 

 of the flower beds ; on the sides of a 

 flower pot in the window ; on the fence 

 posts in the back yard, and luxuriantly 

 in a small aquarium on my microsco- 

 pe table, where it still presented the 

 characteristic massing of the chloro- 

 phyll against the cell Avail. But as an 

 aerial growth it finally became altered 

 in an astonishing way, and revealed a 

 part of another secret, yet with a "miss- 

 ing" link" that I hope to find "some- 

 where, somehow." 



In the late summer or in the early 

 autumn, Ulothrix disappears from the 

 garden beds, and its place is taken by 

 a common moss. Is the alga a stage 

 in the development of the moss ? Do the 

 algal filaments originate from the Pro- 

 tococcns cells, which, as is well known, 

 have no right to separate, generic ex- 

 istence, but which, in this instance, 

 become a terrestrial Ulotlirix, and in 

 favorable conditions, a protonema, and 

 eventually a common moss? Where 

 the Ulothrix is the moss finally appears. 

 The inference is plain, if not convinc- 

 ing, but the succession is too constant 

 to be rejected as meaningless. I have 

 not been successful in my search for 

 a sight of the actual changes. The 

 links between the alga and the proto- 

 nema, and between the protonema and 

 the moss, are missing, yet I am per- 

 suaded that they exist. Perhans some 

 observer more favorably situated in 

 locality and in leisure, not to say in 

 perseverance, may solve the problem. 

 It appears that Ulothrix flaccida when 

 aquatic is an alga, and that when ae- 

 rial the alga finally becomes a moss. 



