738 SUMMARY OF CURRENT RESEARCHES RELATING TO 



t 



those writers who regard colour as of the greatest importance in the 

 attraction of insects. The scent of many flowers is also an important 

 factor, but the present writer disagrees with those authors who make it of 

 primary importance. 



Cleistogamy in Linaria.* — E. J. Hill has studied Linaria cana- 

 densis, with special reference to pollination. The author finds that 

 plants of 10-15 cm. in height are usually cleistogamic, those of 12-15 cm. 

 in height are partially cleistogamic, but have a few small, open flowers, 

 while plants 15-20 cm. high have larger flowers, and only a few cleisto- 

 gamic. The cleistogamic condition is also affected by change in 

 season ; during the spring and early summer the flowers may be 

 visited by insects, and cross-fertilisation is brought about ; but by June 

 the flowers begin to decrease in size, until ultimately they are all cleis- 

 togamic. In dry regions even tall plants bear cleistogamic flowers. The 

 behaviour of Linaria in this respect appears to "be connected with the 

 increase of light and heat and the decrease of moisture. Cleistogamic 

 flowers require less food, and so husband the resources of the plant for 

 seed-production ; also, in cleistogamic flowers the essential organs are 

 better protected. Linaria canadensis is an example of a plant de- 

 generating from a highly-evolved form of insect-pollination to the self- 

 pollination of a cleistogamic condition. 



CRYPTOGAMS. 



Ptericlophyta. 

 (By A. Gepp, M.A. F.L.S.) 



Vascular Structure of Gleichenia. | — L. A. Boodle and W. E. 

 Hiley describe the vascular structure of some species of Gleichenia, espe- 

 cially G. pectinata, which differs from all other members of the genus in 

 having a solenostelic rhizome. The structure of the node is similar 

 to that of G. flabellata, with certain complications due to leaf-gaps and 

 solenostely. The rhizome of G. pectinata branches in two ways, mono- 

 podially in the vertical plane, and dichotomously in the horizontal plane. 

 Eagleichenia represents a series of forms showing reduction from the 

 typical Martensia type, as represented by G. flabellata. Martensia in- 

 cludes the most primitive species of Gleichenia as well as the most 

 advanced, viz. G. pectinata. The solenostelic structure of G. pectinata 

 is to be regarded as derived from a protostelic Martensia type like that 

 of G. flabellata. The course of evolution may have consisted in the for- 

 mation of a pith and ramular gaps, followed by intrusion of phloem, etc., 

 through a ramular gap into the pith and subsequent extension throughout 

 the rhizome. 



Mesarch Structure in Lycopodium.}— E. W. Sinnott gives a sketch 

 of what has been written about the position of the protoxylem in relation 

 to the later-formed elements of the wood in fossil and living plants, and 



* Bot. Gaz., xlvii. (1909) pp. 454-66 (4 figs.). 



t Ann. of Bot., xxiii. (1909) pp. 419-32. 



+ Bot. Gaz.,xlviii. (1909) pp. 138-44 (1 pi.). 



