THE BLADDERS IN OTRICULARIA VULGARIS. 411 
Bladders in sensitive condition were severed from the plant under water 
by cutting through their footstalks. The bladders were then carefully floated 
into a small spoon, taking care throughout not to touch the sensory hairs. 
The spoon, full of water containing bladders, was then removed and immersed 
in Bouin’s Picro-formol, contained in a suitable vessel. The bladders were 
now floated out into the fixative and the spoon removed. After some minutes 
and mixing of the water from the spoon with fixative, a large part of the 
diluted fixative was removed and fresh added in the place of it, so that the 
strength was nearly normal undiluted. Fixation was allowed to take place 
for from twelve to eighteen hours to make sure of penetration, though 
probably much less would have sufficed. After the above period the Picro- 
formol was removed and replaced by 50 per cent. alcohol, the operation being 
carried out with due care, keeping the bladders always immersed in fluid. 
The 50 per cent. alcohol was next replaced by 70 per cent. after an hour or 
so, and all picrie acid was washed out in 70 per cent. alcohol. By similar 
gradual replacement the bladders were carried through 90 per cent. to abso- 
lute alcohol, and then by the method of flotation, with removal of surface- 
layers from time to time, into a mixture of equal parts chloroform and 
carbon-bisulphide. When at last in the pure mixture of chloroform and 
carbon-bisulphide, chips of paraffin-wax of about 40° C. melting-point were 
added and dissolved. The solution of wax when saturated was placed in an 
open vessel on the top of an imbedding oven, outside, in order to drive off 
much of the chloroform and carbon-bisulphide. At last the bladders were 
left in almost pure wax, and were then placed in a bath of wax 52? C. to 
56? C. melting-point within the oven. Two changes were given over a period 
of four to five hours. Sections were cut on a Jung-Thoma microtome, and 
finally stained with Heidenhain’s Iron Hematoxylin, or Delafield's Hæma- 
toxylin counterstained with Biebrich Scarlet. 
In conelusion, I would express my indebtedness and sincere thanks to 
Mr. J. Ramsbottom for his kindness in communicating this paper, and to the 
Staff of the Botany Department, British Museum (Nat. Hist.), for affording 
me every facility and help in referring to literature. 
BIBLIOGRAPHY. 
1. ARBER, A. 1920. Water Plants. Cambridge. 
2. Brocuer, F. 1911. Le probléme de l'Utriculaire. Annales de Biologie lacustre, Tome v. 
pp. 33-46. 
3. Darwin, C. 1875. Insectivorous Plants. Chaps. xvii. & xviii. London. 
4. Kamrénskt, F. 1877. Vergleichende Untersuchungen über Entwicklungsgeschichte der 
Utricularien. Bot. Zeit., Jahrg. xxxv. pp. 761-776. 
5. LuETzkLBURG, P. von. 1910. Beiträge zur Kenntnis der Utricularien. Flora, Bd. c. 
pp. 145-212. 
6. Mert, E. M. 1922. Biologische Studien über die Utriculariablase. Flora, Bd. cxv. 
Heft 1, pp. 59-74. 
7. MoseLey, H. N. (for G. E. Sımms). 1884. Nature, May 22nd, vol. xxx. p. 81. 
8. WITHYCoMBE, C. L. 1916. Observations on the Bladderwort. Knowledge, vol. xxxix. 
no. 581 (New Series, vol. xiii. pt. 12), pp. 238-241. 
LINN. JOURN.—BOTANY, VOL. XLVI. 2u 
