NOTES ON RECENT RESEARCH. 



267 



Strassburger are referred to. The author says that " the above three 

 papers leave the identity of the pollen grain and its ontogeny an open 

 question, since the peculiarities of the division are so different from 

 those heretofore observed in other types, and have led many to believe 

 that a shortening of the process takes place in the members of this 

 genus. It would remain an open question until it was proved that all 

 the divisions concerned, up to and including the formation of the sperm 

 cells, are exactly the same in all essential points in Asclepias as those 

 which occur in other Angiosperms. This identity is established for the 

 first time by the developmental history as traced in the foregoing paper." 

 Thirty-seven good figures are provided. — B. I. L. 



Study of Polygala. 



Polygala polygama and P. paucifolia, Comparative Struc- 

 ture of the Flowers, with Review of Cleistogramy. By Chas. 

 Hugh Shaw, Ph.D. (Contr. Bot. Lab. Phil vol. ii., No. 2, 1901, p. 122 ; 

 pis. 16, 17). — Polygala poly gama develops, in addition to the evident and 

 the subterranean types of flower, a third type — the aerial cleistogamic — 

 which may be found abundantly in midsummer. The last are morpho- 

 logically intermediate between the former two types, and furnish a 

 connected series between the conspicuous and subterranean flowers. 



The shoots bearing aerial cleistogamic flowers are more or less geo- 

 tropic. 



The chasmogamic flowers very largely fail to mature seed. The 

 cleistogamic produce seed abundantly. 



The five sepals are present in all types of flower. Only the 

 anterior petal is found in the subterranean flowers, and the same, with 

 two others, appear in the aerial cleistogamic. Eight stamens are 

 generally present in the aerial cleistogamic, but more or less reduced ; 

 and in the subterranean blooms from three to seven are found, still more 

 reduced. The pistil of the subterranean flowers is greatly reduced, that 

 of the aerial cleistogamic intermediate between the former and the 

 chasmogamic flower : a well-developed nectary in the chasmogamic 

 flower, only traces in the aerial cleistogamic, wanting in the subterranean 

 form. 



Stomata present on all parts of the evident calyx. In extreme 

 abundance on the outer surface of the sepals in aerial cleistogamic, and 

 on the calyx of the subterranean flowers, in a rudimentary condition. 



The microspores of the evident flowers undergo a great increase in 

 size at the time of flowering, which is true to a less degree of the micro- 

 spores of the two other types of flowers. 



The walls of the microspores are very thick. 



A canal is present in the pistil leading from the ovarian cavity to the 

 exterior. 



Glandular hairs, found sparsely on the ovary of the evident flowers, 

 present in great abundance on that of the subterranean, pointing to some 

 kind of specialisation. 



The chasmogamic flowers of P. paucifolia exhibit a condition of 

 initial gynandry, combined with the complete coalescence of stamens and 

 petals. 



