200 
METHODS IN PLANT HISTOLOGY 
broken off after the material has been brought into xylol. If 
whole tufts are imbedded, the branches diverge enough to make 
perfectly longitudinal sections of the apical cells rather rare. Iron 
haematoxylin with a faint staining in orange is a satisfactory com¬ 
bination. 
Ectocarpus.—For general morphological study, branches should 
be mounted whole in Venetian turpentine. A 6 to 10 per cent 
formalin solution (in 
sea-water, of course), 
or the chromo-acetic 
acid will give good fix¬ 
ation. Stain some in 
iron-haematoxylin and 
some in Magdala red 
and anilin blue. 
Mount on each slide 
some from each lot. 
Sporangia usually ap¬ 
pear earlier than the 
gametangia. So col¬ 
lections should be 
made at different sea¬ 
sons. August is rather 
late for sporangia, but 
gametangia are abun¬ 
dant at this time. You 
should have both spor¬ 
angia and gametangia 
on each slide (Fig. 47). 
Desmotrichum.—Forms as large as Desmotrichum can be handled 
like Ectocarpus , but care must be taken not to overstain. 
Laminaria.—-In such large forms, small portions showing the 
structure and development of the thallus and also the reproduction 
should be cut out with a razor and then placed in the fixing agent. 
The sporangia of Laminaria stain very deeply and quickly. Iron- 
haematoxylin is good, but be careful not to overstain. After this 
stain is just right, about 3 to 5 minutes in alcoholic safranin will 
stain the mucilaginous structures and add to the value of the 
preparation. 
Fig 47.— Ectocarpus: A, sporangia (“unilocular spor¬ 
angia”) of various ages; gametangia (“pleurilocular gametan¬ 
gia”), three of them nearly mature. Fixed in 10 per cent 
formalin and stained in iron-haematoxylin. X280. 
