Clathrosorus, a New Genus of Plasmodiophoraceae. 
BY 
C. FERDINANDSEN 
AND 
O. WINGE. 
With Plate XXI. 
HE material of the species here described was sent to us from Sorb, 
JL Sealand (Denmark), by Mr. H. Gram, consulting horticulturist, in the 
month of June, 1918. On roguing bluebells ( Campanula rapunculoides ) 
from his garden Mr. Gram observed that the roots of the named weed often 
showed numerous small swellings, calling in mind to a certain degree the 
bacterial tumours on the roots of leguminous plants (see PI. XXI, Fig. 1). 
Some root-swellings sent to us for closer investigation were fixed in Carnoy, 
and as it proved that we had before us a new and interesting Plasmodio- 
phoracea we made some slides of the material for a more detailed examination. 
Preparations stained with cyanine-gold-orange showed in their cytological 
features a pretty close accordance with the other Plasmodiophoraceae. 1 
We have observed the nuclear divisions in the vegetative stage, whereof 
Figs. 2 and 3 on PL XXI give a pair of pictures, as well as in the akaryotic 
and sporogonic phase ; in the last-named stage we saw both the heterotypic 
and the homoiotypic division. 
The infection falls only on the cortex, whose more peripheric cells 
nearly all contain a single plurinucleate myxoplasma or a sporosorus ; in 
the direction of the central cylinder the number of uninfested cells increases. 
Into the strongly distorted central cylinder itself the parasite never comes. 
The myxoplasma very often is lodging around the nucleus. The cells are 
scarcely hypertrophied by the invasion, but are stimulated to more frequent 
divisions ; as a rule the myxoplasma, respectively the sporosorus, will not 
by far fill out the lumen of the invaded cell. It is further characteristic of 
1 See, e.g., Maire et Tisson : La cytologie des Plasmodiophoracees et la classe des Phytomyxinae ; 
Ann. Myc., 1909. Blomfield and Schwartz: Observations on the Tumours on Veronica Chamaedrys 
caused by Sorosphaera veronicae\ Ann. Bot., 1910. Winge, O. : Cytological Studies in the 
Plasmodiophoraceae; Arkiv for Botanik, 1912. 
[Annals of Botany, Vol. XXXIV. No. CXXXVI. October, 1920.] 
I i 2 
