240 CONTRIBUTIONS TO 
in its individual development that its wall is thickened by 
secondary deposits. 
3. The cytoblasts also remain persistent in the pollen-gra- 
nules in some rare instances ; such is the case in some, perhaps 
in all the Adzetine. The lenticular cytoblast has already been 
observed by Fritsche in Larix europea, but the true nature 
of it was not recognised. 
4, Lastly, many hairs, particularly such as exhibit motions 
of the sap within their cells, retain the cytoblasts (e, f, fig. 25). 
It is at the same time remarkable, and a proof of the close re- 
lation which the cytoblast bears to the whole vital activity of 
the cell, that the little currents which frequently cover the 
entire wall like a network, always proceed from and return to 
it, and that when in statu integro it is never situated without 
the currents (fig. 25). 
I have observed the above-described development of the cells 
throughout its entire course in the albumen of Chamedorea 
schiedeana, Phormium tenax, Fritillaria pyrenaica, Tulipa sylves- 
tris, Elymus arenarius, Secale cereale, Leucoji spec., Abies excelsa, 
Larix europea, Euphorbia pallida, Ricinus leucocarpa, Momordica 
elaterium, and in the embryonal extremity of the pollen-tube 
of Linum pallescens, Cinothera crassipes, and many other plants. 
It was in the summer of 1837, after this treatise had been 
written, that I first began to examine the Leguminose, and 
found to my surprise that these plants, so constantly imvesti- 
gated and everywhere employed as illustrations for the history 
of vegetable development, afforded the most beautiful and ready 
opportunities for the study of this process, which had been 
overlooked by all observers. No one, however, had considered 
the saccharine fluid contained in the embryonal sac as worthy 
of examination. 
Without exactly tracing the entire course of the formation of 
the cells through all its details, I found the cell-nuclei, previous 
to the appearance of the cells, floating loose in the fluid in 
very many plants. Finally, I have not met with a single ex- 
ample of newly-developed cellular tissue, the cambium excepted, 
in which the cytoblasts were wanting. I therefore consider that 
I am justified in assuming the process above described to be 
the universal law for the formation of the vegetable cellular 
tissue in the Phanerogamia. 
