Fex. 1909.] | BOTANICAL SOCIETY OF EDINBURGH 35 
Puate V., 
Fig. 1. Tillandsia dianthoidea, T.S., a normal root. The lateral 
thin parts of the cortical sheath are due to the emergence 
there of secondary roots. 
» 2. Piteairnia bracteata. Heterodera Q in situ in endodermal 
gall, apparently slightly doubled. Note the isolated 
thickened cell. 
., 3. Pitcairnia corallina, badly attacked root. The endodermis 
and vasa have been occupied. 
,, 4. The same, more highly magnified. 
EXUBERANT LENTICEL FORMATION ON AN OAK SEEDLING. 
By Miss BertHa CHANDLER, M.A., B.Sc. (Plate VI.) 
At a former meeting of the Botanical Society Mr. 
Rutherford-Hill showed an oak seedling which had been 
sown in water, exhibiting, in consequence, abnormally de- 
veloped lenticels on the roots. The specimen, which was 
eleven weeks old, was kindly given me by Mr. Rutherford- 
Hill, with another, seven weeks old. The photographs are 
from the former, the older specimen, which exhibited these 
outgrowths to a more marked extent than the latter. 
Before examination under the microscope, these structures 
were thought to be “pneumathodes,” but sections showed 
that they were rather lenticels having no differentiated 
structure apart from the lateral root which these encircled. 
The production of abnormal lenticels is very much akin to 
the artificial production of aerial roots, for the same factor, 
excess of moisture, favours the development of both struc- 
tures. Just as pneumathodes can be induced in plants by 
cultivation under water, so abnormal lenticel formation, 
caused by the accelerated division of the lenticel initials, 
can also be induced. The oak seedling figured is an 
example. Terras,! speaking of abnormal lenticels occurring 
on stems, says that under similar conditions the same thing 
occurs on roots. The two main factors, the abundance of 
moisture and the reduction of the pressure owing to the 
slight resistance of the medium in which the seedling is 
grown, account for the abnormal development of these 
1 “Trans. Bot. Soc. Edin.,” xxii. p. 450. 
