﻿I9i6] CURRENT LITERATURE 87 



Rafflesia and its host. — Brown 1 ' has made a study of the relation of 

 Rafflesia manillana to its host, a species of Cissus. It is parasitic on the roots, 

 the base of the flower being imbedded in a vase-shaped mass of tissue formed 

 from the root of the host. The vegetative portion of Rafflesia consists for the 

 most part of rows of cells, which occur in the xylem, medullary rays, cambium, 

 phloem, and sclerenchyma of the host. The flowers originate from rows of 

 cells which usually cross the cambium. The presence of the parasite causes 

 an excessive growth of both the xylem and the bark of the host, resulting in the 

 formation of the vase-shaped mass of tissue in which the base of the shoot is 

 imbedded. The differentiation of the growing point takes place before the 

 shoot breaks through the bark of the host, but the enlargement of the parasite 

 finally produces cracks in the bark, through which the parasite grows. — 

 J. M. C. 



Sex determination— Wilson 20 has studied material of Mnium hornum in 

 which an axis bears heads of "mixed organs" and also female heads. Some of 

 the organs resembled antheridia, others archegonia, while a complete series of 

 intermediate forms also occurred. Since the spermatogenous cells of the 

 normal antheridia possess six chromosomes, the normal gametophyte number, 

 the plant could not have been produced aposporously. The conclusion is 

 suggested that sex determination is not bound up with mitosis, but is brought 

 about "by metabolic processes which operate in the organism over a con- 

 siderable part of its life history." Thisi 1 " 

 and the conditions of living is a point of vi 

 established as the facts of sexuality accu 



ae of them covered by ; 

 alga. Since these specimens were obtained from a depth of 150 ft 

 determination of the alga was of considerable interest. Upon refer* 

 Collins and Brand, the alga proved to be Cladophora profunda Bi 

 species occurring in the lakes of the Bavarian highlands, but at no 

 depth than 15 meters. Brand characterized the Lake Ontario mat< 

 "forma ima." The species has not been recorded hitherto In Ameri 

 the depth at which it occurs is three times as great as any before kn 

 J. M. C. 



«' Brown, W. H., The relation of Rafflesia manillana to its host. Phil. Jour. Sci. 

 Bot. 7:209-226. pis. 12-21. 1012. 



"Wilson, Malcolm, Sex determination in Mnium homum. Ann. Botany 29: 

 443-440. pi. 20. 1915. 



" Kindle, E. M., Limestone solution on the bottom of Lake Ontario. Amer. Jour. 

 Sci. 39:651-656. figs. 3. I9i5- 



