34

Scientific Memoirs by

genus, but on a study of their life history it was evident that this was not the
case, but that they were representatives of a closely allied and apparently as yet
undescribed one.

     The leaves of Limnanthemum indicum in which they occur are charac-
terised by the enormous number of stomata in the superior epidermis and by
the presence of comparatively large substomatic spaces between the subjacent
palisade cells (Plate III, fig. 4). Due to this the tissue immediately beneath the
superior epidermis is of an extremely open, almost reticulate character (Plate
III, fig. 6). The algal cells are absolutely confined to the substomatic spaces
which they deform in various ways as they increase in size and press upon the sur-
rounding tissue elements. Beyond the distortion arising in this way, the presence
of the foreign bodies produces no appreciable effect on the tissues save causing
a permanent wide patency of the stomatic orifices. There is no sign of injury
of the surrounding palisade and ordinary parenchymal cells, which in general
aspect and amount of chlorophyll content differ in no respect from those in
areas which have not been invaded by the alga. Due to the mutual pressure of
the algal and host cells many of the former in many cases gradually lose their
originally evenly rounded contour and come to present irregularly lobed or
even angular outlines. They naturally vary very considerably in size accord-
ing to the stage of development, but mature green specimens give an average
of 59 µ by 50 µ. On making vertical sections of the affected leaves the rela-
tions of the algal cells to the surrounding elements appear very clearly. They
press laterally on the neighbouring palisade cells and above are in close contact
with the stomatic openings and the under-surfaces of their guard cells (Plate III,
fig. 5).

     The cells differ greatly in appearance in different cases, as has been already
mentioned, and this difference is connected with their age and with the ultimate
developmental changes which they undergo in connection with seasonal influ-
ences. Young cells have a delicate cell-wall surrounding a thin layer of pale
green protoplasm within which is a great colourless area containing a single
nucleus. Amyloid granules are present in gradually increasing numbers in the
peripheral green layer (Plate III, fig. 3). The green colouring increases in inten-
sity and extends more and more into the central portion, and the contents thus
gradually become of a uniform deep green and of coarsely granular consistence.
On removing the colouring matter with alcohol and subsequently staining the
presence of a single nucleus is still demonstrable up to this stage. Repeated
processes of nuclear division now set in and the contents are thus gradually
converted into a continuous mass of protoplasm, including a very large number
of distinct nuclei (Plate III, fig. 8). A differentiation of the cytoplasm now
occurs and each nucleus becomes gradually invested by a separate layer proper
to itself, the entire mass of contents as the process goes on coming to present
a lobulated, mulberry-like appearance. The nucleated protoplasts which have