ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 79 



a lower, usually smaller, basal cell, and an upper and larger apical 

 cell. A second wall follows almost immediately in the apical cell, 

 meeting the first usually at an angle of 45°. The succeeding divisions 

 meet the basal wall of the apical cell at the same angle in alternate 

 directions. The division of a segment-cell is always preceded by the 

 accumulation and turbidity of the contents ; and after this again 

 becomes clear, an extremely fine membrane is to be made out only 

 with difficulty by the position of the chlorophyll-grains or by intense 

 illumination. Further divisions could be followed out only in a single 

 instance. 



The product of the divisions in the prothallium of L. inundatum is, 

 therefore, as de Bary has observed, a cellular structure consisting of 

 an axial row of cells bounded at the base by the basal cell, above by 

 the apical cell, and at the two sides by two rows of crescent-shaped 

 cells. The fullest development observed amounted to four cells in 

 the axial row, and in the two rows of crescent-shaped cells, together 

 with the apical and basal cells. The contents consist of a few chloro- 

 phyll-grains and an evidently granular nucleus. The length of a 

 10-celled prothallium was from 0- 081-0 -099 mm., with a breadth 

 of 0-059-0 -062 mm. No indication of reproductive organs was 

 observed. 



Germination and Sexual Generation of the Marattiaceae.* — The 

 development and structure of the prothallium of the Marattiaceae has 

 at present been only very imperfectly observed. Jonkman has now 

 succeeded in following the germination of the spores, of which there 

 are two kinds. By far the larger number are bilateral, interspersed 

 with a few of a cubico-spherical form. The surface is covered with 

 minute wart-like spines ; the wall is transparent and colourless, and 

 is composed of three layers — the endospore, the exospore, itself 

 divisible into two or three layers, and the epispore or perispore, each 

 showing a different colour with different reagents. 



The bilateral spores of Marattia germinate in seven or eight, 

 the cubical and bilateral spores of Angiopieris in five or six days. 

 They at once develop chlorophyll, first in cloudy masses, afterwards 

 in granules. The exospore bursts, and the first cell of the prothallium 

 projects like a papilla between the two lobes ; this gradually increases, 

 and becomes rounded off into a ball five or ten times the size of the 

 spore. Numerous divisions of the chlorophyll-grains take place in it. 

 After about four weeks, the first cell-division takes place at right 

 angles to the axis of growth ; the first rhizoid, which, like the suc- 

 ceeding one, is never brown, having made its appearance just before. 

 In the next stage of division the quadrant-walls are formed, followed 

 by the octant-walls, so that the normal prothallium soon becomes a 

 mass of cells, distinguished from the prothallia of typical ferns by 

 its deep green colour and moderately thick cuticle. The fui'ther 

 development of the prothallium usually proceeds from the four upper 

 octant-cells. One of the quadrant-cells usually becomes the apical 



* Arch. Neerland. Sci. exact, et natur., xv. (1880). See Bot. Centralbl., i. 

 (1880) p. 900. 



