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THE AMERICAN NATURALIST [Vol. XLI 



of the male gametophyte, which is the most primitive yet discovered 

 among the seed bearing ])]ants. The fully devel()i)ed pollen tube 



rise to sixteen large s()enn;itozoi(ls similar to tliose known in several 

 other genera of cxcad-.. In exceptional cases as many as ten body 

 cells were noted. ' WhcthcM', as s(vnis j.robable, the eight body cells 



The male gamciophu.- of Mi.To. j. ,hus i,een to be less reduced 

 than that of M)nic li(M<T()^poron> ])tcridoj)hytes, e. g. Isoetes, Salvinia, 

 AzoUa, while no otlier living seed plant is known to show more than 

 two generative cells, unless possibly Araucaria, where a large number 

 of nuclei have been reported in the pollen tube, the exact nature of 

 which, however, is somewhat problematical. 



The (level()[)nient of the female gametophyte was not followed in 

 detail, but it was found that the number of archegonia is very large, 

 sometimes exceeding two hundred. So far as could be determined, 

 the archegoniuin is of the same type as that of the other cycads. 



The ripe seed contains a single large, straight embryo, with three 

 to six cotyledons. The young plant produces a tuberous stem several 

 centimeters in length before the first true leaf emerges. The author 

 concludes that :\Iicrocycas is the most primitive of all the known 

 cycads. Th(> paper is illustrated by a number of excellent photo- 

 graj)hs and there arc tUrvv plates showing the tnost important points 

 in the developnuMit of the gametophyte. 



The remarkable series of fossil cycads from different regions in the 

 United .States, but especially from the Black Hills of Wyoming and 

 South Dakota has been exhaustively treated in the magnificent memoir 

 by Wieland (American Fossil Cycads. G. R. Wieland. Carnegie 

 Institution of Washington, No. 34, 1906). Space will not permit a 

 com])lctc review of this volume, which comprises nearly three hundred 

 quarto pag(>s, with fiftv plates and many text figures. The work is 

 mainl^ ba^.l upon tin- great collections in the museum of Yale Uni- 



