80 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cell, the rejuvenescence of which continues until the prothallium has 

 assmned its ultimate cordate form. 



In Marattia the antheridia appear in five, in Angiopteris in four 

 months, on both the upper and under surfaces of the prothallium, but 

 neither on the margin nor (as Luerssen maintains) on the lateral lobes. 

 They are formed within the tissue of the prothallium, and never pro- 

 ject above its surface. Their structure is quite different from that in 

 the typical ferns, and even from that in Osmundacese. From a single 

 prothallium-cell there are produced, by successive divisions, a central 

 cell, two outer cells, and a three-cornered stigmatic cell, which is thrown 

 off when the antheridium is mature. Within the central cell are 

 formed from twenty to two hundred antherozoid mother-cells. 



About ten months after the spores are sown, both in Marattia and 

 Angiopteris, the archegonia make their appearance on the under, and 

 sometimes also on the upper surface of vigorous prothallia, but exclu- 

 sively on the median cushion-like thickening. They resemble those of 

 Ophioglossum or Salvinia more closely than those of typical ferns, pro- 

 jecting above the prothallium only by the two uppermost rows of cells 

 of the neck. Their development takes place as follows : — A superficial 

 cell of the prothallium, the mother-cell of the archegonium, divides 

 into two daughter-cells by a wall parallel to the surface, the upper one 

 being the mother-cell of the neck, and the lower and larger one the 

 central cell. From the former are formed, by two successive divisions 

 at right angles to one another and to the surface, four cells, each of 

 which becomes the mother-cell of a row of neck-cells. The central 

 cell divides by a bulging wall into a lower cell, termed by Jonkman 

 the ventral cell, and an upper neck- canal-cell. The ventral cell 

 divides subsequently into two daughter-cells, the upper of which be- 

 comes the ventral canal-cell, and the lower one the oosphere. Both of 

 these, as well as the lower rows of neck-cells, become gradually sur- 

 rounded by a number of small cells capable of swelling — the mantle- 

 cells. The antherozoids were seen by the author forcing their way 

 into the open neck of the archegonium, and some of them disappearing 

 in the neck-canal ; but their history was not traced any further. 



This knowledge of the sexual generation of the Marattiacese appears 

 to widen their separation from the typical ferns ; but their true 

 systematic position cannot yet be determined with certainty. 



Muscineae. 

 Structure of Orthotrichum.* — Venturi has made an exhaustive 

 examination of this difficult genus of mosses, especially with reference 

 to the simplicity or duplicity of the peristome, the number of teeth in 

 the peristome, the presence of appendages to the cilia of the inner 

 peristome, the nature of the cells of the leaf, &c. In classifying the 

 species he also lays great stress on the variation in the nature of the 

 stomata in the capsule, whether lying in the same plane as the epider- 

 mis (phaneroporous), or depressed beneath it [cryptoporous), and on the 

 correlated position of the peristome-teeth in the dry state, whether 

 erect and spreading radially, or recurved towards the outer surface of 



* Rev. Bryol., vii. (1880) pp. 65-76. 



