THE HIGHER CRYPTOGAMIA. 57 



mentary stem observed in the germination of different 

 species. One apical cell divides continually by septa alter- 

 nately inclined in different directions. In Jungermannia 

 bicuspidata, and Frullania dilatata, these septa are directed 

 alternately right and left; the apical cell has the form 

 of a segment of a sphere. The cells of the second order 

 are divided by radial longitudinal septa. In each of 

 the three-sided daughter-cells a septum is formed, cutting 

 the side walls at an angle of 45, and dividing the cell into 

 an inner and an outer one. The latter is divided by a 

 radial longitudinal septum into two halves ; the growth of 

 the circumference, even in leafy shoots, terminates at this 

 point in J. bicuspidata and many nearly allied species, such 

 as J. connivens, and divaricata. In these species both layers 

 of cells, but more frequently only the outer one, continue 

 to divide by horizontal septa; the four inner cells again 

 divide by longitudinal septa, parallel to the axis ; and after- 

 wards at least two, often four of the newly- formed narrow 

 cells of the interior of the stem, divide by radial septa. 

 The axis of the stem consists, consequently, of somewhat 

 elongated cells, which are much narrower than those of the 

 single cortical cellular layer. Hence, also, there arises the 

 indication of a vascular bundle, traversing the longitudinal 

 axis of the stem. At a similar stage of the development of 

 the stem in thickness the lowest which occurs in the 

 vegetable kingdom, from the leafy mosses upwards the 

 germ-plants of all observed species make a stand ; ultimately 

 and by degrees thicker shoots are formed, which produce 

 the rudiments of fruit. 



The great variety of forms in the leaves of Jungermannia 

 is only partly accounted for by the rules of development of 

 their cells. Many of the most striking varieties of form in 

 perfect leaves are produced by an anomalous expansion of 

 small groups of cells, and a multiplication, commencing at 

 a late period, in individual cells of the margin of the leaf. 

 The same difficulties which interfere with a clear ascertain- 

 ment of the structure of the terminal bud, hinder to a still 

 greater extent the observation of the first stages of develop- 

 ment of the leaves. I have only been able in a few cases 

 to observe directly that the leaf originates in the continual 



