VAUCHERIACE. 117 
B. Between the antheridia and thallus itself is found a shorter empty 
boundary cell (not containing chlorophyll). 
@ ANDROPHOR, Several horn-shaped bent antheridia placed 
on a swollen cell containing chlorophyll, which is fixed to 
the side of the thallus, by meansof the boundary cell. 
12. V. synandra, Woron. 
6 PILOBOLOIDE#, Antheridia bordering immediately on the 
boundary cell (frequently provided with several mouths). 
aa Oogonium bordersimmediately on thethallus branch. 
* Several fructification tubes on the 
oogonium, 
13. T. coronata, Nordst. 
** Oogonium with only one fructification 
opening, but the antheridia with 
several. 
+ Oospore round. 
14. 7. intermedia, Nordst. 
15. V. spherospora, Nordst. 
+ t Oospore lens-shaped. 
16. V. piluboloides, Thur. 
db Below the oogonium a boundary cell. 
17. V. litorea, Hofm. 
Place uncertain. 
18. 7. tuberosa, Br. 
19. 7’, trifurcata, Kutz. 
The sexual reproduction in Vaucheria has been minutely described by 
Pringsheim, of which we give an abstract. Vaucheria, besides the 
asexual multiplication by zoospores also exhibits a true sexual propaga- 
tion, effected by means of the two organs known as the “ hornlets” and 
the spores, the latter being more correctly termed “sporangium.” Both 
organs arise like papillary branches from the tube, and in close proximity. 
It isusually the case that the papilla destined to become the hornlet is 
formed sooner than that in which the sporangium originates. The two 
papille even from the first differ so widely in dimensions, that they can 
scarcely be confounded. The papilla which becomes the hornlet soon 
elongates into a short cylindrical slender branch, which at first rises 
perpendicularly from the tube, then curves downwards until it comes in 
contact with the tube, often forming a second, or a third curve, and in 
this way always represents a more or less stunted branch, which fre- 
quently exhibits several spiral turns. The papilla of the neighbouring 
sporangium usually begins to appear at the time when the hornlet is 
commencing its first turn; but the period at which it arises is very 
indeterminate, for it sometimes appears much earlier, whilst the hornlet 
is still perfectly straight, sometimes much later after it has curved, so as 
to form two limbs of equal length. 
The papilla destined to become the sporangium gradually enlarges 
into a considerable-sized lateral out-growth of the tube, far exceeding the 
hornlet in width, whilst in length it is barely equal to the straight limb 
of the latter. This out-growth which is afterwards symmetrical, 
ultimately throws out a beak-like prolongation on the side looking 
towards the hornlet, the rostrum of the sporangium, whence the latter 
acquires its peculiar form, resembling that of a half developed vegetable 
ovule. Up to this period the hornlet as well as the sporangium are not 
shut off from the tube by any septum ; the cavity of the hornlet and that 
of the sporangium consequently remain uninterruptedly continuous with 
the parent tube, and are filled with similar contents. A number of 
chlorophyll granules inan albuminous plasma and rounded oil globules, 
constitute a dense lining to the tube, the sporangium, and the hornlet. 
Between this aud the cellulose membrane is the thin colourless cutaneous 
layer. 
