98 MOSSES AND FERNS CHAP. 



The differentiation of the capsule and seta follows as in 

 Aneura, and the arrangement of the cells of the archesporium 

 is much the same except that the rows of cells radiate from the 

 base of the capsule and not from the summit. The foot is 

 very distinct and forms a pointed conical cap, whose edges 

 overlap the base of the seta. 



Spore-division in Anacrogynce 



According to Farmer (4), in Pallavicinia decipiens there is 

 formed, previous to the division of the nucleus, a "quadripolar" 

 nuclear spindle, extending into each of the four lobes of the 

 spore mother-cell. Then follows a double division of the 

 chromosomes, resulting in sixteen, of which four move to each 

 pole of the spindle to form at once the four nuclei of the spore 

 tetrad. In Aneura niultinda the formation of a quadripolar 

 spindle was also found, but there were subsequently two suc- 

 cessive nuclear divisions of the usual type. From his study of 

 Pellia epiphylla, Davis (3) has questioned the accuracy of 

 Farmer's statements, and Moore's ( i ) studies on Pallavicinia 

 Lyalii show that in this species, although a structure which 

 might be interpreted as a quadripolar spindle is present, there 

 are two successive divisions of the nucleus with bi-polar spin- 

 dles. However, the second mitosis follows without an inter- 

 vening resting stage of the nucleus. 



The growth of the seta after the spores are ripe is ex- 

 tremely rapid, but consists entirely in a simple elongation of 

 the cells. Askenasi (i) has investigated this in Pellia epi- 

 phylla, and states that in three to four days the seta increases 

 in length from about i mm. to in some cases as much as 80 

 mm., and that this extraordinary extension is at the expense 

 of the starch which the outer cells of the young seta contain 

 in great abundance, but which disappears completely during 

 the elongation of the seta. The growing sporogonium here as 

 well as in other species is strongly heliotropic. 



The calyptra in the thallose Anacrogynae is usually massive, 

 and in addition there is formed about the growing sporogo- 

 nium a special envelope inside the involucre, which in Palla- 

 vicinia especially (Fig. 41, A) becomes prolonged into a tube 

 which completely encloses the sporogonium until just before its 

 dehiscence. 



