OF ARTS AND SCIENCES. 211 



from view by the surrounding tissue. At this stage all the cells are 

 filled with a finely granular protoplasm, and it is not until later that 

 the cyst-cells lose their contents. 



The further development of the head consists in an increase in the 

 size of the spore-mass, accomj^anied with an enlargement of the cyst- 

 cells and an elongation of the stem (Fig. 14). As the spore-mass 

 develops, the outer walls of its cells continue to thicken, and at matu- 

 rity assume a rich chestnut-brown color. The cyst-cells expand, and 

 finally lose their contents. The stem, usually at quite a late period, 

 becomes considerably lengthened, and the head, assuming the matured 

 form, is lifted above the surface of the leaf. 



In the course of the development of the head no feature has pre- 

 sented itself which cannot be easily harmonized with the proposition 

 that the head is a bundle of fused hypha3, bearing spores. In fact, 

 since the earlier stages show the filamentous nature of the head more 

 plainly than the more advanced conditions, and since a study of these 

 stages explains how that arrangement is disguised in the mature head, 

 it is evident that the course of development not only does not oppose 

 our former hypothesis, but doubles the argument in favor of it. As a 

 final statement concerning the morphological nature of the head, we 

 may therefore assert, that, from the anatomy of both the matured and 

 developing head, the structure is essentially that of a cluster of fused 

 teleutosporic stalks, individually equivalent to a stalk and teleutospore 

 of such a form as Puccinia, and collectively equal to a cluster of the 

 same. 



Having reached the above conclusion concerning the morphology of 

 the teleutosporic stage of Ravenelia glandulceformis, it remains only 

 for us to conclude with some notes upon a few of the other species of 

 this genus. As preliminary to these, a short historical review of what 

 is already known of these species may not be inappropriate. 



With the exception of a recent paper by Mr. M. C. Cooke, the con- 

 tributions to the literature of Ravenelia have been rather of a syste- 

 matic nature than otherwise, and, although more or less anatomical 

 detail is necessary in such work, still it must be remembered that 

 anatomy was not the end sought for, but rather a necessary accom- 

 paniment. 



The Rev. M. J. Berkeley first called attention to the genus Ra- 

 venelia, and in a short paper* gave descriptions of two species, R. 

 Indica, Berk., and R. glandulosa, Berk, and Curt. The following 



* The Gardeners' Chronicle, p. 132, 1853. 



