330 SUMMARY OF CURRENT RESEARCHES RELATING TO 



by a leaf-lobe of normal appearance. The first is a common variation ; 

 the sporophylls are of healthy appearance, and occur in the most 

 vigorous parts of the hest shoots. A comparison with the Spheno- 

 phyllalcs seems the most promising way of considering these variations. 

 The leaves of Splienopliyllnm weie often heteromorphic, and among 

 great variety in form we find those with a dichotomously branched 

 blade, and in some forms the bracts were forked. In S. tricliomatosum 

 the sporophylls were not arranged in sharply delimited cones. The 

 second group of variations recalls the case of JBoicmanites, where the 

 bracts bore sporangiophores, each with two sporangia. Trilocular 

 synangia may occur in Tmesipteris, and this suggests comparison with 

 the elaborate palmately tripartite sporangiophore of Cheirostrobus. The 

 third class of variation supports the comparison of the synangium with 

 a ventral leaf-lobe. 



The author suggests a parallel botween Tmesipteris and the Spheno- 

 phyllales on the one hand, and a simple Lycopodium such as L. Sehujo 

 and Lepidodendron on the other. The contrast in the leaf-arrangement, 

 whorled in Sphenophyllales and scattered in the Psilotese, is marked, 

 but can hardly outweigh the evidence derived from sporangial cha- 

 racters. In Psilotum also instances were found of dichotomy of one or 

 both forks of the sporophyll, with corresponding increase in number of 

 the synangia. 



So-called Phloem of Lepidodendron.* — A. C. Seward reiterates 

 his opinion as to the absence of any true secondary phloem in Lepido- 

 dendroid stems. He maintains that his " secretory zone," while pro- 

 bably having phloem functions, does not, as Weiss has recently de- 

 scribed, show phloem structure, and we cannot therefore, as suggested 

 by Scott, regard the phloem of Lepidodendron as fundamentally similar 

 to that of the recent allies of the genus. The author also shows that 

 the tissue immediately beyond the secondary wood, which Scott regards 

 as phloem, can, by comparison of transverse with longitudinal sections 

 (of which he gives figures), be shown to form a homogeneous band of 

 short thin-walled cells, in which the formation of new cell-walls was in 

 active progress when the plant was killed. Its structure is essentially 

 distinct from that of typical phloem, and there are no elements which 

 can be compared with sieve-tubes. It is, in fact, a broad, meristematic 

 zone of quite a different type from the cambium of recent plants. 



Mosses. 



Spore Distribution, f — A. J. M. Garjeanne discusses the spore- 

 distribution as it occurs in a few mosses. In Pottia Heimii the opercu- 

 lum splits off from the gymnostomous theca in the presence of moisture 

 after dry weather, but remains attached to the columella ; and the spores 

 are spread by the slightest currents of air, or by the movements of 

 insects. In P. truncata and Physcomifrium pyriforme, both gymno- 

 stomous, the operculum is completely detached in the former, and 

 partially split off in the latter ; aud in the latter the spores of different 

 individuals differ in their capacity for germination. The distribution 



* New Phytologist, i. pp. 3S-5G (2 figs.). 



t Beiheft. Botan. CentralbL, xi. (1901) pp. 53-9. 



