206 FIRST FORMS OF VEGETATION. 
plication of the Roman numeral x, and in other 
cases resembles a series of the letter v ; the spiral 
rings after conjugating producing a dark coloured 
globule in one of the filaments. The spiral, it may 
be remarked, is the first regular form which falls un- 
der the notice of the unassisted vision, and unites 
in itself the two principles of unity and variety. 
In the inner surface of the cell it may be seen first 
of all; and all the parts of the plant subsequently 
added, whether microscopic or visible, assume this 
form. So universal is the spiral tendency through- 
out the vegetable kingdom, that, beginning with 
the cotyledons or seed-lobes, the whole of the 
appendages of the axes of plants,—leaves, calyx, 
corolla, stamens, and carpels, form in their normal 
state an uninterrupted spiral, governed by laws 
which are nearly constant. It is very interesting 
to trace in the obscure and humble organisms 
under consideration, the order and harmony which 
are so characteristic of the highest works of crea- 
tion, which are in striking accordance with the 
native principles of beauty implanted in the human 
mind, and which proceed, we must believe, from 
Infinite Wisdom. The Zygnemas form the prin- 
cipal fresh-water algze of India, occurring in pools 
and streams in the central districts, as well as 
among the Himalayas. They ascend as high as 
15,000 feet on these mountains, forming cloudy 
