J 9i2] LANTIS— ABUTILON THEOPHRASTI 331 



microsporangia in an anther, Abutilon resembles Althaea (2, 4), 

 Hamamelis (13), Elodea (12), the Asclepiadaceae, etc. 



In cross-section the archesporium is a single hypodermal cell 

 (fig. 1). An apparent exception to this was observed in a few 

 cases where two or three hypodermal cells, because of their size 

 and reaction to stains, might be considered archesporial in their 

 possibilities. The subsequent history of the anther, however, 

 shows that there is only one true archesporial cell as seen in cross- 

 section. While a longitudinal section of the archesporium was 

 not observed, it is very evident that it consists of a single row of 

 several cells, since such a section shows the primary parietal and 

 primary sporogenous cells lying in single rows the full length 

 of the anther (fig. 2). This condition in Abutilon agrees with 

 that reported for the Malvaceae and most Compositae, and also 

 tor Gaura (14). The archesporial cells divide, as usual, by peri- 

 clinal walls to form the primary parietal and primary sporogenous 

 ce "s (fig- 3). 



The primary sporogenous cells initiate two successive divisions, 

 one radial and the other periclinal (figs. 4 and 5). Each primary 

 sporogenous cell, therefore, as a rule produces only four mother 

 cells, these four cells being almost regularly shown in a cross- 

 section of the microsporangium (fig. 5). Thus there is quite a 

 contrast between Abutilon and Althaea rosea (2), since in the latter 

 only a single mother cell is usually to be found in a cross-section 

 of the microsporangium, and in Malva also the mother cell is 

 reported to develop directly from the primary sporogenous cell. 



As may be seen from fig. 4, there are usually two parietal layers 

 m the stage immediately preceding the formation of the mother 

 cells. Fig. 5 shows the spore mother cell just previous to the 

 tetrad formation. At this stage there are three parietal layers 

 including the tapetum, which is well developed. In its origin the 

 tapetum is like that of Asclepias Comuti (10), Silphium (9), 

 and other forms; and the same account is evidently true for 

 Althaea, as may be judged from Sachs's figure (2, fig. 377). The 

 tapetum reaches its highest development about the time of the 

 tetrad formation, as is true in most angiosperms. Its develop- 

 ment is much later than that of the tapetum of Euphorbia (8). 



