120 MR. HENFREY ON THE DEVELOPMENT 
layer lining the wall, others lying in the more internal parts - Be — Mop s 7 
some cases the chlorophyll globules are so closely packed, in ~ ate iem : Mh es 
parenchymatous form from mutual pressure (fig.14). Thesec — : g - : : 
in a high degree those characters found in the same gars in a ; ies g - = e 
gamous plants,—characters which appear to warrant Nageli S- view tha e chlorophy 
is contained in a membranous vesicle, and that these vesicles are increased m number by 
a process of subdivision like that of cells. I have met with appearances which I cannot 
explain in any other way, but shall be content wath a mere indication here, to avoid 
digressing from the immediate subject of this Memoir. I believe that I have seen the 
enveloping membrane enclosing a green fluid (fig. 15) ; moreover, the development of two 
or more starch-granules inside those vesicles, so as gradually to displace the chlorophyll ; 
but as the vesicles are only about 3555th or 15-555th of an inch in diameter, much careful 
examination is requisite before a safe decision can be arrived at. 
In some cells I have seen a small colourless and formless accumulation of mucilage 
upon the side wall, among the chlorophyll globules. It is possible that this may have 
been a nucleus. I also found a large clear and circular vesicle in one of the cells of an 
old barren prothallium ; this had all the appearance of a nucleus, excepting that it was so 
exceedingly transparent. In the vegetative cells generally I saw no trace of nuclei. 
The cells of the older posterior part of the prothallium contain but little chlorophyll, 
and like the root-filaments, are filled with colourless, slightly granular mucilaginous fluid ; 
and they often appear stained with brown patches, arising from the partial decay of the 
walls. In all cases the death of the cell-membrane is followed by a brown colouring of 
the dead part. | 
Such is the normal history of a prothallium, so far as its vegetation is concerned (for 
the reproductive structures, left out of view in the preceding description, are in part deve- 
loped at a very early period). -If the regular development of a leafy stem takes place, a 
term is naturally set to the existence of the prothallium, which quickly decays away as 
the young stem grows up. But if the prothallium remains barren, if none of the arche- 
gonia become fertilized, its vegetative existence may be continued for a long time. The 
lateral lobes grow much larger, their borders become curved and sinuous, or variously 
convoluted; new lobes sometimes grow out from the cushion-like thickening in the 
middle; and, finally, individual 
development exhibited by the spore-cell in the original germination, so as to produce new 
prothallia (by a process of budding), which become detached from the parent (fig. 12). 
The progeny of * proliferous ' prothallia exhibit antheridia, but I have never seen arche- 
Jona upon them. In other 
respects they are exact repetitions of the parent structure. 
x SEO every stage of the growth of the prothallium, in some cases from the time 
form h x tection of some dozen cells, in others not until the cordate 
as become evident he latest period; so that since they run through their 
