STUDIES IN THE DEVELOPMENT OF THE PIPERACEAE 721 
be used, in the case of Piper betel, at least, to indicate any onto- 
genetic process of union occurring after the sporogenous ce^^s are 
once distinguishable. 
If the normal stamen of angiosperms is to be regarded as pos- 
sessingfour microsporangia — a view generally accepted — then it is 
evident that in the case of certain of these abnormal stamens we 
are warranted in saying that the development of one or more of 
the microsporangia is completely suppressed. The tissue, which 
in the normal stamen organizes the sporogenous mass, may in 
another fail to show any such specialization of its cells. On the 
other hand, we have seen that the tissue of the region which usu- 
ally forms the connective may occasionally give rise to sporogen- 
ous cells, and thus form a continuous pollen mass across from theca 
to theca (figs. 25, 29, 31). 
In the above description I have spoken generally of sporogen- 
ous masses, instead of sporangia. The question naturally arises 
here whether each distinct sporogenous group, with its continuous 
tapetum and wall, is to be regarded as an individual sporangium. 
In stamens, such as are illustrated in figs. 9 and 26, one must admit 
it would seem, that two microsporangia are present, and that each 
corresponds exactly, in location and development, to one of the 
four sporangia of the ordinary stamen. When however, we at- 
tempt to determine the number of sporangia in stamens such as 
are shown in figs. 21, 24, 25, 27, 28 and 29, the solution of the 
problem is not so evident. If we accept the definition of sporan- 
gium given by Bower ('08, p. 112), that an individual sporangium, 
in vascular plants, consists essentially of '^an isolated spore- 
mother-cell, or a connected group of them, or their products — 
together with its protective tissues," then in the stamen shown in 
fig. 27, for example, there is but a single microsporangium pres- 
ent. For there is a single continuous mass of sporogenous cells 
completely surrounded by a tapetum. If, on the other hand, we 
note the position and extent of the sporogenous mass, and its 
partial division by a septum, it then seems evident that it is in 
position and extent the equivalent of two of the sporangia of an 
ordinary stamen. For the same reasons, the sporogenous mass 
of the stamen shown in fig. 29 may be considered the equivalent, 
THE JOURNAL OF EXPERIMENTAL ZOtH.OGY, VOL. 9, NO. 4. 
