﻿ON THE GENUS CROOMIA. 455 



cylindrical cells, as shown in Fig. 6. Long before the seed matures, each of theae 

 hairs or rows of uniserial cells becomes a much thicker and longer thread or band, 

 more or less club-shaped towards the extremity, and composed of a tissue of cells 

 (Fig. 12). Some of these threads are now found to originate from the rhaphe, but 

 far the greater part of them belong to the funiculus. 



Upon a re-examination of the minute embryo, taken from well-matured seeds, the 

 obscure nick which had before been discerned at its larger or cotyledonar extremity, 

 was found to be eccentric. The figures 13 and 14 exhibit the embryo under the micro- 

 scope, as it appeared to Mr. H. J. Clark, who kindly furnished these figures. As the 

 views obtained by Mr. Sprague and myself, although not so clear, were not essentially 

 different, we conclude that the embryo is monocotyledonous. 



The structure of the stem is more ambiguous. The woody bundles which compose 

 the whole fibro-vascular tissue of the proper stem above ground, from seven to ten in 

 number, as seen in a transverse section, stand strictly in a circle, thus dividing the 

 general parenchyma into a central medullary and an external cortical portion, just as 

 in the seedling or nascent stem of an herbaceous Exogen. Indeed, the whole appear- 

 ance is far more like the exogenous type than is that of the stalk of Podophyllum, 

 in which the somewhat similar bundles are irregularly dispersed. 



In Croomia, however, the anatomical structure of the individual bundles does not 

 accord with that of ordinary exogenous bundles. These remain as definite threads, 

 cylindrical or nearly so, and separated by uncompressed parenchyma, although two ad- 

 jacent bundles are occasionally confluent into a broader double one ; and there is no 

 appearance of a cambial stratum dividing each bundle into an outer and an inner por- 

 tion, answering to liber and to wood. But — so far as revealed by a rather superficial 

 examination, under moderate powers of the microscope — each separate bundle con- 

 sists of nascent or cambium cells in the centre, surrounded by a zone of thick-walled 

 elongated cells, the inner ones apparently bast-cells, and the outer common prosen- 

 chyma ; this in turn surrounded by a , complete, or nearly complete, zone of ducts, 

 commonly uniserial and the greater part scalariform ; and this by a more or less definite 

 and thin layer of prosenchyma or wood-cells. These woody bundles, therefore, — al- 

 though peculiar, and worthy of detailed examination by a phytotomist, — appear to be 

 endogenous, or at least not exogenous, in type. 



In the rhizoma, the more abundant fibro-vascular tissues form a complete and closed, 

 although somewhat irregular, zone of wood, surrounding a small but well-defined pith, 

 and itself surrounded by a broad parenchymatous cortical portion (the parenchyma of 

 both loaded with starch) ; thus closely imitating the exogenous structure. But there 



