Kashyap. — Notes on Equisetum debile, Roxb . 443 
tapering downwards and disappearing first above the origin of the first leaf- 
traces. In other words, considered from below, it arises immediately after 
the giving off of the first leaf-traces. Each of these leaf-traces, like the 
traces higher up in the adult stem, have their own endodermis. 
The significance of the islands of parenchyma surrounded by endo- 
dermis is not quite clear. Probably they represent vestiges of bundles 
which have gradually disappeared owing to the habitat of the plant, which 
is generally swampy soil. It is interesting to compare in this connexion 
the condition of the normal vascular bundles, which are also greatly reduced 
and partly replaced by air-spaces. 
3. The Prothallium. 
The writer published an account of the structure and development of the 
prothallium of Equisetum debile in 1914 ( c Annals of Botany ’, January 1914). 
The material of that investigation was obtained chiefly from the river bank, 
where the prothallia grow in large numbers, and only the youngest stages 
were observed by growing spores in the laboratory. Last year as well as 
this year spores were germinated and prothallia were allowed to go on 
growing for several months, and some interesting observations were made. 
In some experiments spores were made to germinate at some distance from 
each other (by shaking some spores in water and sprinkling a little of this 
water on the soil in the pot, which was watered from below), leaving plenty 
of room for the growing prothallia, and it was observed that all the pro- 
thallia grew large, having a circular outline, bore archegonia only at first, and 
attained a diameter of nearly 3 mm. in forty-five days. They went on 
growing and some are growing even now (January 1917), having been pro- 
duced from spores sown in November last. Even the very young stages 
showed a meristem all along the circular margin, and this meristem is always 
present along the whole margin in the bigger specimens. In a few cases, 
however, it was found that the prothallium showed a more vigorous growth 
on one side and the meristem was localized on a part of the margin. This was 
probably due to the mode of germination, owing to the spore having formed 
a short filament first, while in the other case it formed a mass of cells. 
Even in those cases where the meristem was localized on a part of the 
margin in the young stage, it would have gradually spread to the rest of 
the margins also, as shown by some other specimens which were a little 
older. 
In other experiments the spores were grown thickly. In these it was 
observed that the prothallia grew in thick clusters and remained very small 
even after two to three months. They showed a distinctly apical growth 
and the meristem was restricted to one part of the margin. Naturally the 
prothallia were elongated antero-posteriorly, and the largest were about one 
H h 
