TRANSACTIONS OF SECTION K. 845 



Liquid preservatives are invaluable for the preservation of the form, but their use 

 involves a sacrifice of the natural colours. 



Characters of colour, however, have not as a rule the same morphological im- 

 portance as have characters of form, so tliat preFerving by drying is rarely 

 resorted to. 



Turning to liquid preservatives, all do uot preserve the form of plants equally 

 well, and it is important to distinguish those preserving only the form and shape 

 of the separate parts from those preserving, not only the form of the separate 

 organs, but the relationships of the parts to one another also. Expressed con- 

 cretely, the separate leaves on a twig, their shape, substance, and form, may be 

 well preserved in a given medium ; but unless there is also preserved the correct 

 angle at which the leaves stand out from the stem, and their relationships to one 

 another in leaf symmetrj--, then the preservation of the form of the specimen is of 

 a limited kind. Again, the value from this point of view of any preservative 

 differs somewhat according to the character of the specimens to be preserved. 

 These may be grouped as follows : — 



1. Herbaceous plants and organs which in the natural state owe their shape 

 and firmness to the turgescence of the cells more than to special strengthening 

 tissues. Such specimens flag and become soft when that turgescence is lost. For 

 these sti'ong alcohol has given by far the best results. It penetrates auicldy 

 and fixes by dehydration the shape and position of the parts before changes due to 

 loss of turgescence occur. Formaline may preserve well the form of the separate 

 parts, but the specimen remains soft and the organs flaccid and drooping. 



2. Woody structures, twigs, roots, &c. For these alcohol or an aqueoi's 

 raediimi answers equally well. The choice of one or auotlier is determined by a 

 consideration of the ultimate method of exhibition. 



3. Succulent plants, succulent fruits, and all bulky specimens containing rela- 

 tively large quantities of water. Alcohol if employed for these often causes 

 contraction. Formaline or some other aqueous medium is to be preferred, as such 

 penetrate less readily and exert a less energetic attraction for the contained water. 



II. Bleaching. — Specimens which darken in the alcohol or formaline in which 

 they are preserved are bleached by one or other of the following methods: — 

 {a) By immersion in hot or boiling water ; {!/) by means of acid alcohol; (c) by 

 the use of bleaching solution (hypochlorite of lime). To prevent as far as possible 

 the darkening in alcohol the specimens are immersed in the preservative as soon as 

 gathered, and when possible exposed at once to direct sunlight. 



III. Mounting. — The specimens are attached to thin clear glass by means of 

 photoxylin or gelatine, the glass being cut to fit the rectangular vessel in which 

 the specimens are to be exhibited. The back of the vessel is painted a suitable 

 colour, or coloured glass is placed behind the clear glass. Never is the specimen 

 mounted direct upon blue or opal glass, as this renders impossible a change 

 of background should the continued bleaching or darkening of the specimen 

 demand it. 



The naming of the parts of the specimen is accomplished as follows : — 



1. The parts named are pointed out upon the specimen itself by means of 

 pointers made of ihin glass tubes containing colouring matter to render them 

 conspicuous ; or 



2. _A photograph or drawing of the specimen is made, and the names of the 

 parts indicated upon this. 



2. The Anatomy q/ Ceratopteris thalictroides (Brongniart). 

 By Sydille O. Ford, Neionham College, Cambridge. 



Ceratopteris thalictroides is the single memlier of the Parkeriacete. It is an 

 annual aquatic fern which occurs in the tropics, either rooted in the mud or 

 floating freely. 



The stem" i8 much reduced ; sterile as well as fertile leaves are found, botiv 



