2S0 SUMMARY OF CUURENT RESEARCHES RELATING TO 



gouiatPD, which does not correspond to any affinity of structure. The 

 or"an known as the archegonium in these two chisses has no doubt the 

 same function, and they resemble one another so far that the mother- 

 cell of the oogonium divides into two cells, the lower of which becomes 

 the oosphcre ; but here the resemblance ceases. The archegonium of 

 Muscineic, to which alone the tei-m ought strictly to be confined, is 

 axial instead of epidermal in its nature, and the paraphyses by which 

 it is surrounded are of a foliar character. 



The archegonium of ^luscinea) always originates from a single 

 primordial mother-cell, which after its separation from a lower cell by 

 a transverse wall, produces, by further divisions, the oosphere, the 

 canal, and their common envelope. These divisions are eifected by 

 three longitudinal walls, two anticlinal and one periclinal, separating 

 an axial cell from which spring the oosphere and the canal-cells, 

 and three peripheral cells, the origin of the archegonium-sac. The 

 lowest of these cells, Janczewski's " central cell," never undergoes 

 more than one further division, giving rise to the oosphcre or " em- 

 bryonal cell," and above it to the " ventral canal-cell." The second 

 ceil, the " primary canal-initial-cell," produces a row of cells varying 

 in number, but always some multijjle of four, by bipartitions in basi- 

 fugal succession. The successive divisions up to the complete deve- 

 lopment of the oosphere are always the same in the entire group, and 

 present a great contrast to the corresponding phenomena in Vascular 

 Cryptogams. 



The sporogonium which results from the fertilization of the 

 oosphere does not form an alternating generation with the sexual 

 plant in the sense in which the phrase is used with respect to Vascu- 

 lar Cryptogams ; the perfect development of both proceed in parallel 

 lines. The sporogonium is composed of the urn (sporangium), the 

 seta, and the foot. The two latter organs differ greatly in their 

 development according to (1) the direction in which it takes place ; 

 (2) the time at which it occurs ; (3) the result to be attained. The 

 seta is the support of the sporogonium, and supplies it with the 

 nutrient material which it is the sole function of the foot to absorb. 

 The envelope of the sporangium varies in its origin. In the 

 Andreeeacese it proceeds from the enlargement of the primitive arche- 

 gonial sac ; elsewhere it is due, partially or entii-ely, to the develop- 

 ment of neighbouring organs. The author proposes for this structure 

 the term epigone. 



Thecalyptra is an organ of Mosses alone, not occurring in the Hepa^ 

 ticse. The vaginnle in Mosses varies greatly in its origin. It some- 

 times consists of the persistent base of the epigonial sac ; sometimes 

 it is formed simply from the growth of the tissues of the mother- 

 plant. 



The Muscinefe constitute a primary division distinct from Vascular 

 Cryptogams, characterized by the following peculiarities : — (1) The 

 ai'chegonium is altogether different from that of Vascular Cryptogams ; 

 (2) they are the only plants which produce a fruit of sexual origin 

 giving rise, by differentiation of their tissues, to spores of endogenous 

 origin. The Muscinese divide themselves naturally into the Musci and 



