8 BOTANICAL GAZETTE [JULY 
' gcalariform tracheids of the lepidodendroid stems is paralleled 
by the same structures in the transitional primary wood of Arau- 
caria. They do not urge this point as a strong argument, but 
merely point out that the presence of the two distinct types of 
pitting in the mature secondary wood of the two groups does not 
“necessarily imply separate lines of descent.”” The resin canals 
of the araucarians can be derived as well from the mucilage cells 
and canals of the Lepidodendreae as from those of the Cycado- 
filicales. 
They are strongly of the opinion that the multicellular pollen 
grains of the araucarian alliance are very different from those of 
Cordaitales or any other recent seed plants. They differ from the 
former in the arrangement of the cells, and from the latter in the 
much greater development of the vegetative cells. A comparison 
with the microspore of Selaginella or Isoetes appears more convin- 
cing. The reduction they ‘‘connect with the substitution of sipho- 
nogamous for zoidogamous fertilization, which would demand as 
much space and material as possible for the production of the 
pollen tube.”’ 
STILES (61) argues that the conifers can be derived more readily 
from the lycopods than from the Cordaitales. His argument is 
divisible into two parts: (1) an attempt to show that Podocarpeae 
(and hence other conifers, for he holds that all have had a common 
origin) cannot have been derived from Cordaitales and must, 
therefore, have been derived from the only other(?) available 
source, the lycopods; and (2) a direct comparison of conifers and 
lycopods to show the possibility of deriving the former from the 
latter. 
Under the first head he adduces much excellent evidence to show 
that the podocarps are closely related to the araucarians. He 
also attempts to show that the conifers are monophyletic. The 
next step is to show that podocarps cannot have been derived from 
Cordaitales, in consequence of which the other conifers are likewise 
excluded from such an origin. He enumerates four points which 
he considers sufficient to preclude the possibility of the primitive 
podocarps having originated from Cordaiteans: (a) the stem of 
these podocarps is no more like that of the Cordaitales than it is like 
