THE PSILOTALES 



unusual malformation of the spindle was found at meiosis in many of the spore mother 

 cells, which resulted in tripolar or quadripolar figures at the first division (Fig. 234c) and 

 from six to eight nuclei at the end of the second. This abnormality was thought to be 

 metabolic rather than cytological in origin, since it is not a normal attribute of tetra- 

 ploidy as such, but it confuses the interpretation of the prothallial structure by intro- 

 ducing a possible source of genetical abnormality into their make-up. This risk may be 



A: 





t 



J ' ♦ 



'•^•t.«f 





Fig. 234. Tetraploid sporophyte of Psilotum nudum (L.) Beauv. (P. triquetrum Swartz) all after Manton 

 (1942). a. Tip of a fertile twig of a sporophyte from Rangitoto Island decolorized in alcohol, x 2. 

 b. Mitosis in a tetraploid rhizome from Malay in which a chromosome count ('over 200') was 

 made, x 1000. c. Group of four mother cells showing in-egular meiosis with a tripolar spindle 

 from the Rangitoto material, x 500. 



thought of as more apparent than real, since spores as irregular as those observed are 

 most unlikely to have been viable, and reproduction of the species could easily be con- 

 fined to the normal mother cells which were also present. The fact of polyploidy, how- 

 ever, at once disclosed the need for further investigation of both generations on wild 

 material. 



It is at this point that Professor Barber's recent observations are of special interest. He 

 reports that material growing wild near Sydney, Australia, is also tetraploid. This means 

 that Darnell Smith and Lawson's (1917) source of prothalli is hkely to be of the same 

 general type as that on Rangitoto Island and a true haploid is still to seek. Further, 

 Professor Barber made the interesting observation that meiotic irregularities involving 

 tripolar spindles were also encountered by him at Sydney on wild material fixed after a 

 spell of unusually cold weather, but that the same material after transfer to the laboratory, 



238 



