THE BASIS OF SEX INHERITANCE IN 

 SPH^ROCARPOS. 



By CHARLES E. ALLEN. 

 (Read April 25, 1919.) 



Sph.^rocarpos in Cultivation. 



The studies here described were made upon cuhures of Sphcr- 

 rocarpos Donnellii Aust. growing under greenhouse conditions. 

 Through the kindness of Dr. A. B. Stout, living plants of this spe- 

 cies were received from the New York Botanical Garden on Jan- 

 uary 13, 1916. These plants, as Dr. Stout informed me, had been 

 obtained from Mr. Severin Rapp, Sanford, Florida. To a request 

 for additional material Mr. Rapp very generously responded, as he 

 has to later similar requests, and the greater part of my present 

 cultures of this species began with material which he sent. Plants 

 have been received from Mr. Rapp on February 4 and March 10, 

 1916, on January 21 and February 23, 1918, and on April 10, 1919. 

 On February 16, 1916, plants of Sphcerocarpos were obtained for 

 class use from the Plant Study Company, Cambridge, Massachu- 

 setts. A letter from the company informed me that they had been 

 collected at Miami, Florida, by Miss Clara Hart. Some of these 

 plants were used also as starting points for greenhouse cultures. 

 Plants of all the cultures here referred to have been identified as 

 those of 5. Donnellii, and this identification has been confirmed by 

 Miss Caroline C. Haynes, to whom were sent representatives (in- 

 cluding sporophytes) of each set of cultures except those derived 

 from the last lot of plants supplied by Mr. Rapp. 



My experience has shown that the thalli of 5". Donnellii (and of 

 S. texamis Aust. as well) can be kept growing indefinitely, the pos- 

 terior portions dying as growth continues at the anterior end. This 

 applies to the gametophytes of both sexes, although the male thalli 

 are much more susceptible to unfavorable conditions and it is only 

 with some care and difftculty that cultures of the male plants can be 



PROC. AMER. PHIL. SOC, VOL. LVIII, S, AUG. 7, IQIQ. 289 



