637 
no such single originating layer exists, that thè rows must grow by 
intercalary divisions only. The indications of thè mode of thè growth 
of thè callosity were not sufficiently pronounced to permit me to come 
to a definite conclusiori. Prora an examination of some of my material 
Schmitz was able to satisfy hìraself as to thè mode of thickening and 
to conclude that it is thè sanie as in thè thickening of thè midribs 
and veins of other NitophyllecBy and Delesseriece as described by hira 
in a paper which appeared in 1892 ^). Schmitz sees no signs of in- 
tercalary divisions in thè formation of thè vertical rows of cells of 
thè callosity but considers thè rows are added to by thè repeated 
cross-division of thè outer terminal celi of each row on both sur- 
faces of thè thallus, in fact that thè rows of cells forming thè callosity 
are uniseriate filaments^ closely cemented together and growing by 
their apical cells. Thus if this view be adopted (and 1 must say thè 
evidence of its correctness is by no means convincing to me), thè mode 
of growth of thè callosity is simply an application of Schmitz ’s 
well-known theory of construction of thè Floridean thallus *). Por 
thè simplicity and ingenuity of this theory I bave, I hope I raay 
say without presumption, much admiration but before it can be gen- 
erally accepted as a working basis in thè classìfication of thè Flo^ 
ridece it should be rigorously applied to as many and as varied genera, 
and different parts and stages of genera, as possible. Admitting for 
thè moment that Schmitz is correct, that thè growth of thè cal- 
losity is frora without, by thè repeated cross-division of thè superfi* 
cial cells of thè rows, this is no more than occurs in thè thickening 
of thè raidrib of thè Browu Alga D/c/yop/gr/s, which is, as is admitted, 
parenchyraatous in nature. (Here, however, intercalary divisions in thè 
inner cells of thè midrib occur no doubt). It does not, then of necessity 
follow that thè rows of cells of thè callosity are uniseriate cellular 
fìlaments cemented together, even though each row be added to by 
thè repeated cross-divisions of its outer terminal celi. Schmitz him- 
self fìnds that his theory cannot be applied to thè apical gi’owth 
of thè thallus of Nitophyllum versicolor. He then proceeds to a 
restateraeut of his reasoiis for thè proposed exclusion of thè Bangia- 
cete from thè Rhodophycece, using as a starting point for his re- 
marks my observation: «Before Schmitz can apply his theory to thè 
9 Fr. Schmitz: Kleinere Beitràge zur Kenntniss der Florideen, I (La Nuova 
Notarisia, serie III, 1892). 
9 Fr. Schmitz: Untersuchungen ùber die Befruchtung der Florideen, 1883, 
