240 CONTRIBUTIONS TO 



in its individual development that its wall is thickened hy 

 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 Abietince. The lenticular cytoblast has already been 

 observed by Fritsche in Larix europaa, 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 (c,/, 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 Chamcedorea 

 schiedeana, Phormium tenax, Fritillaria pyrenaica, Tulipa sylves- 

 triSjElymus arenarius, Secale cereale, Leucoji spec, Abies excelsa } 

 Larix europcea, Euphorbia pallida, Ricinus leucocarpa, Momordica 

 elaterium, and in the embryonal extremity of the pollen-tube 

 of Linum pallescens, Oenothera 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 Leguminosce, and 

 found to my surprise that these plants, so constantly investi- 

 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. 



