72 SUMMARY or CURRENT RESEARCHES RELATING TO 



communicating pits in the contiguous walls of the tracheids and tbe- 

 parenchyma-cells of the ray. There is also a radial elongation and 

 projection of the ends of the vertical tracheary elements in a direction 

 parallel to and in contact with the parenchymatous cells of the ray,, 

 with communicating pits in the intervening walls. As true ray-tracheids^ 

 do not occur, it is believed that these structures are acting as such, and 

 possess all the functions attributed to and carried on by ray- tracheids.. 

 In many cases the course of the bent and prolonged tracheid is imitated 

 by those immediately contiguous with greater or less development. 

 These structures are similar to those described by Thompson in the 

 cone-axis of Finns Sirobus, and by Jones in the mature wood of 

 Sequoia semperviretis, A. B. R. 



Reproductive. 



Staminate Strobilus of Taxus canadensis. — A. W. Dupler {Bo(^ 

 Gaz., 1919, 68, 345-66, 3 pis., 22 figs.). In a previous paper {Bot. 

 Qaz.^ 1917, 64) the author has described the gametophytes of this 

 species. The development and vascular anatomy of the staminate 

 structures are here treated. 



The staminate strobili occur in the axils of the leaves. The buds 

 may first be distinguished from other types of buds by the broad apex. 

 The sporophyll primordia first appear as slightly rounded lobes above 

 the general surface, and may arise in acropetal succession. The arche- 

 sporial initials are hypodermal cells and develop according to the 

 eusporangiate method. There are 4-8 of them, distributed around the 

 margin of the primordium. The sporogenous tissue reaches the mother- 

 cell stage about October 1, and forms microspores about two weeks later. 

 There is no abortion of sporangia such as occurs in Torreya, the 

 sporangia occurring in a circle around the stalk of the sporophyll. The 

 sporangium-wall is usually two-layered. The tapetum arises from the 

 peripheral layer of the sporogenous tissue and persists until after 

 megaspore-formation. The epidermis of the sporangium remains alive 

 and thin-walled at the base, dehiscence being accomplished by the 

 rupture of these cells at maturity, by the elongation of the stalk of the 

 sporophyll. Owing to the disintegration of the sporangium-wall,, 

 the epidermis is the functional wall in the later stages. The strobilus. 

 matures in the latter part of April. Just before maturity there is an 

 enlargement and elongation of the axis, pushing the sporophylls beyond 

 the scales. The strobili of Taxus canadensis are somewhat smaller than 

 those of T. baccata. The strobilus-bundles are collateral endarch,. 

 excepting in the terminal portions of the scale-bundles and the sporo- 

 phyll-bundles, where they may be mesarch, and in the latter show 

 indications of occasional exarch structure, the terminal portion of these 

 bundlcK also being concentric. A. B. R. 



