88 SUMMARY OF CURRENT RESEARCHES RELATING TO 



less liquid, having a sweetish taste, and principally gum, and Mr. 

 Meehan has often met with cases where no insects could be found, 

 as well as others where insects were numerous, and where in the 

 latter case, the attending circumstances were strongly in favour of the 

 conclusion that the liquid covering was the work of insects. He con- 

 siders that few scientific men have any knowledge of the enormous 

 amount of liquid exuded by flowers at the time of opening, and he 

 has seen cases where the leaves were as completely covered by 

 the liquid from the flowers, as if it had exuded from the leaves, as 

 he considers Dr. Hoffman had good grounds for believing is often 

 the case. 



What is the object of this abundant exudation of sweet liquid and 

 liquid of other character from leaves and flowers ? We are so accus- 

 tomed to read of nectar and nectaries in connection with the cross- 

 fertilization of flowers, that there might seem to be no room for any 

 other suggestion. But plants like Thuja and Ahies are anemo- 

 philous, and, having their pollen carried freely by the wind, have no 

 need for these extraordinary exudations, from any point of view con- 

 nected with the visits of insects to flowers. In the case of Thuja, Sachs 

 has suggested another use : " The pollen-grains which happen to fall on 

 the opening of the micropyle of the ovules are retained by an exuding 

 drop of fluid, which about this time fills the canal of the micropyle, but 

 afterwards dries up, and thus draws the captured pollen-grains to the 

 nucellus, where they immediately emit their pollen-tubes into its 

 spongy tissue. In the Cupressine^, Taxinese, and Podocarpere, this 

 contrivance is sufficient, since the micropyles project outwardly ; in the 

 Abietinese, where they are more concealed among the scales and bracts, 

 these themselves form, at the time of pollination, canals and channels 

 for this purpose, through which the pollen-grains arrive at the micro- 

 pyles filled with fluid."* 



In his former observations on liquid exudation in Thuja and other 

 plants, Mr. Meehan vp^as inclined to adopt the suggestion of Sachs 

 as to the purpose of the liquid supply ; but as it was present in Ahies 

 so long after fertilization must have taken place, and as it was held 

 up in the deep recesses of the scales of the pendent cone, where it 

 could hardly be possible the wind could draw up the pollen, we 

 must look for other reasons, which, however, do not yet seem to be 

 apparent. 



Latex of the Euphorbiacese.t — S. Dietz has studied the composi- 

 tion of the latex of various plants, especially of the EuphorbiaccEe. 

 He finds almost invariably crystalline substances to be present which 

 crystallize out when the latex is made to coagulate under the cover- 

 glass. In the Euphorbiacege he distinguishes three kinds of crystalliz- 

 able substances, as follows : — 



1. Sphaerocrystals. These differ in their mode of development 

 from any hitherto known. In the coagulated latex of the EuphorbiacesB 



* Sachs' ' Text-book of Botany,' 2nd Engl, ed., 1882, p. 513. 

 t M. Tud. Akad. Ertek., xii. (1882) 23 pp. (2 pis.). See Bot. Oentralbl., xvi. 

 (1883) p. 132. 



