XIV L YCOPODINE.E 



49' 



This, like that of Isoetes, is quite destitute of chlorophyll, and 

 is entirely dependent upon the food materials in the spore for 

 its further development. About this time also bc^n'ns the cell- 

 formation in the part of the spore below the (liaphraf,mi (Fig. 

 256). This is simply a continuation of the same process by 

 which the apical tissue was developed, but the cells arc lar^^^cr 

 and more irregular. 



The archegonia are produced in considerable numbers, and 

 apparently in no definite order. Their development corre- 

 sponds with that of Lycopodiiun, but the neck is very short, 

 like that of the Marsiliaceae, each row of neck cells having but 

 two cells. No basal cell is formed, and the central cell is 

 separated from the diaphragm only by a single layer of cells. 

 The neck canal cell (Fig. 256) is broad, like that of Isoctcs, 

 but the nucleus does not, apparently, divide again. The egg 

 (Fig. 256, E) shows a distinct receptive spot, and the nucleus is 

 clearly defined. At this stage the diaphragm is very evident 

 and much thickened, so that the archegonial tissue of the 

 prothallium is very sharply separated from the nutritive tissue 

 below. 



TJie Embryo 



The first division in the fertilised ovum is transverse, and 

 as in Lycopodium the cell next the archegonium neck becomes 

 the suspensor. This in Selaginella is much more developed, 

 however, and grows at first more actively than the lower cell 

 from which the embryo proper arises. The upper part of the 

 suspensor enlarges somewhat, and forms a bulbous body, which 

 completely fills the venter of the archegonium. The suspensor 

 grows rapidly downward, penetrating the diaphragm and push- 

 ing the young embryo down into the mass of food cells which 

 occupy the space below it. The suspensor is very irregular 

 in form, and undergoes several divisions (Fig. 256, G). 



The first division in the embryo proper is almost vertical 

 (Fig. 256, F), and divides it into nearly equal parts. Beyond 

 this the early stages of the embryo were not followed by the 

 writer, but to judge from the later stages, they correspond to 

 those of 6". Martensii, which has been most carefully studied 

 by Pfeffer,^ and the substance of which may be given as follows. 

 After the first wall is formed in the embryo, there arises in 



1 Pfefter (I). 



