Strobilus in A rchegoniate Plants . 351 
sterilization of the sporogenous tissue. In the Onagraceae the 
stamens of most genera of the order are of the ordinary quad ri- 
locular type ; but in the genera Circaea } Gaura> Clarkia , and 
Eucharidium , the four loculi are each divided transversely by 
one or more sterile septa: these septa may consist of only 
a single layer of cells having the character of tapetum, or of 
two layers, or even of four or more, of which the middle layers 
then resemble the tissue of the connective : an examination 
of the early states of development supports the conclusion that 
the septa result from sterilization of part of the sporogenous 
tissue, for in sections it is seen that the sporogenous cells, and 
those which will form the septa, originate from a common 
layer corresponding to the archesporium of normal anthers. 
A similar state of things has been described by Rosanoff, and 
by Engler in certain of the Mimoseae, in many of which it is 
well known that there are eight pollen-sacs (species of Inga , 
Calliandra , Acacia , and Albizzia), while in others, e.g. Parkia , 
the number maybe much larger. These Engler (Pringsh., Jahrb. 
x. p. 289) recognizes as being all merely variations of the one 
fundamental type with one row of primary mother-cells of 
the pollen at each angle of the anther: certain cells of these 
rows, developing as sterile tissue, provide the septa by which 
the four typical pollen-sacs are partitioned into eight or more 
loculi. From these examples we might proceed also to those 
of Viscum, of some species of Loranthus , and of Rhizophora : 
as the result of developmental study of the latter it is stated 
by Warming (Engler, Jahrb. Bd. 4. p. 519) that the multi- 
locular condition is easily explained by arrest of development 
of parts of the sporogenous tissue, and formation of sterile 
septa. Probably a similar developmental explanation will be 
found to apply in certain other cases, e.g. Aegiceras i Phajus , 
Bletia , and Rafflesia , all of which have multilocular anthers. 
Since such septation resulting from partial sterilization is thus 
shown to occur in pollen-sacs of Angiosperms, it will, I think, be 
futile to deny the possibility of its having occurred also in lower 
forms : the question therefore becomes one of probability only. 
It will probably be remarked that this occurrence of 
