of Fossil Plants of the Coal-Measures . 321 
spots ; hence we cannot apply Reess’ explanation to their 
origin and nature. 
The question, may these objects have a fungoid character, 
suggests itself. Of all the hundreds of host-cells that I have 
examined no one has contained the slightest trace of a 
hyphal filament, hence the presumption against the fungoid 
idea is a strong one. Assuming the accuracy of this 
reasoning, and yet remembering that the objects in question 
must have had some sort of an origin, the question arises can 
these cells be algoid ones ? In the second edition of the 
English translation of Sachs’ Text-book of Botany, we have at 
p. 247 some remarks that may bear upon the question. After 
referring to the fact that colonies of Nos toe have long been 
known to exist within the cavities of cryptogamic plants, in 
some of which cases the germs developed into round balls, 
the author adds, ‘ The entrance of Nostoc into the parenchyma 
of a dicotyledonous plant, Gunner a, is brought about, accord- 
ing to Reinke, in a different manner ; the deeper lying cells of 
the outer part of the stem, themselves covered by layers of 
parenchyma, are densely filled with colonies of the Alga/ 
Now if the germs of a Nostoc could thus find their way into 
the deeper layers of a cortical tissue, there is no reason why 
another and lower unicellular Alga should not be able to do 
the same. Whether or not this is the true explanation, the 
fact that during the Carboniferous age some unicellular vege- 
table organisms did find their way even into the deeper cortical 
tissues of various plants of high organisation is certainly true, 
and the instance of the Gunnera appears to present the 
nearest approach that living plants have hitherto supplied to 
what has occurred in the Carboniferous ones. 
But the still more curious cases of the macrospores, like 
Figs. 14 and 15, remain for consideration. When record- 
ing these instances in my memoir referred to above, I was 
strongly inclined to believe that what I then spoke of as endo- 
sporal cells were normal developments from an endosporal 
protoplasm. And I am still far from certain that this idea is 
not a true one. At the same time the absence of all similar 
