124 RECORD OF CURRENT RESEARCHES RELATING TO 



the division of tlio cells parallel to the surface is the border. The 

 term stoma (Spaltoffiiung) itself he avoids using, because the structure 

 in Marchantiaceee is equivalent only in a physiological sense to the 

 stomata of higher plants. Even without examining the history of 

 their development, it is obvious that, while in ordinary stomata with 

 their guard-cells a bilateral type of structure prevails, all the cell- 

 divisions in the guard-cells of the Marchantiaceae take place radially 

 or in concentric circles. 



The author describes in detail the varieties of structure observed 

 in different genera, the description being accompanied by a plate, and 

 thus classifies the variations in the genera observed by him : — 



A. The guard-cells form a border to the stoma. 



a. The border consists of five rings of cells : the inner pore is 

 broad, and usually square : — Marchantia (jtolymorpha). 



h. The border consists of four rings of cells ; the inner pore is 

 a long cruciform crevice : — Preissia (commutata). 



B. The guard-cells do not form a border to the stoma. 



a. Upper layer of green cells in the stoma with a hyaline 



rostrum destitute of chlorophyll : — Fegatella (conica). 

 h. Upper layer of green cells without such a rostrum. " 

 a. Guard-cells sharply differentiated, arranged in one or more 

 concentric circles or polygons. 

 * Three or more circles of guard-cells, 

 t Walls of epidermal cells angularly thickened ; three or 

 four more or less elongated polygons of guard-cells, 

 usually consisting each of seven or eight cells, the whole 

 with well-marked radii, and considerably larger than in 

 Marcliantia polymorpha : — Beboulia (Jiemisphcerica). 

 If Wall of epidermal cell not thickened or annularly. 



I Three regular polygons of guard-cells, with seven or 

 eight radii ; the whole about as large as in 

 M. polymorpha (F. pilosa has only two, often in- 

 distinct polygons) : — Fimhriaria. 

 II Four rings of guard-cells ; the whole mass usually twice 

 as large a^ in M. polymoryha : — Lunularia (vulgaris). 

 ** One or two circles of guard-cells. 



t Walls of epidermal cells, with the exception of the 

 guard-cells, annularly or angularly thickened. 

 I Walls of epidermal cells angularly thickened ; pore 

 larger than in M. polymorplia : — Targionia (Michelii). 

 II Walls of epidermal cells annularly thickened ; pore as 

 large or larger than in M. polymorpha: — Grimaldia 

 (barhifrons). 

 It Walls of epidermal cells, with the exception of the guard- 

 cells, not thickened ; environment of pore clear : — 

 Sauteria {alpina). 

 (3. No sharply differentiated ring of guard-cells ; the pores 

 appear only as perforations of the epidermis caused by 

 resorjition ; stomata broad, enclosed by layers of a loose 

 green tissue : — Dnvalia (rupcsfris). 



