ZOOLOGY AND BOTAXY, MICROSCOPY, ETC. 275 



their assumed analogy with the Dasycladefe having heen disproved by 

 the recent discovery of the mode of reproduction of the latter.* In 

 some respects they exhibit most relationship to the Yaucheriese. 



The Diatomaceas are undoubtedly most nearly allied to the Con- 

 jugatse, but their true position must for the present remain doubtful. 



The Cryptophycese or Schizosijores, to which the Schizomycetes 

 are undoubtedly closely allied, form a well-defined group, characterized 

 by their structure, the formation of spores and hormogonia, and the 

 presence of phycochrome. 



In an accompanying comparative table, the author arranges the 

 Chlorophycege in four parallel columns, one of which leads to the 

 Bryophyta, Pteridophyta, Gymnospermia, and Angiospermia ; while 

 the Phseophycefe, Rhodophyceae, and Fungi occupy one column each 

 springing at different stages from the Chlorophycese ; and the whole 

 originating from the Cyanophyceas and Schizomycetes. The whole 

 vegetable kingdom can be again arranged in ascending series in six 

 stages, viz. 1. Agamas (or Cyanophyce^) ; 2. Isogamas ; 3. Oogamae ; 

 4. Carposporese (these three stages including the remainder of 

 the Thallophytes) ; 5. the Archegoniatae (divided into Isosporas 

 or Bryophyta, Pilices, and Lycopodiaceae, and Heterospor® comprising 

 Ehizocarpeae and Ligulatae) ; and 6. Anthophyta or Gymnospermae 

 and Angiospermae. 



Cryptogamia Vascularia. 



Development of Sterile Sporangia in Isoetes laeustris.t — Of 



the three methods by which the sterility of these sporanges is 

 caused, E. Mer states that (1) arrest of development takes place 

 by the cessation of the growth of the sporange, even before the 

 formation of trabeculas ; the cells of the formative tissue remain 

 unaltered, and exhibit no starch. Growth may cease after the trabe- 

 culae and hypodermal layer are formed ; the formative tissue-cells 

 have multiplied and become enlarged, but all growth ceases before 

 they become separated. Finally, the spores may even be formed, 

 only to shrivel up. Eeduction of temperature is the cause of arrested 

 growth, which has been observed chiefly in the variety sporifera. 

 Invasion of the formative hy the nutritive tissue is another method (2), 

 which is chiefly noticed in the forms sporifera and gemmifera, and 

 appears to be caused by cold, as in the former case. Its essence 

 consists in the great development assumed by the hypodermal layer and 

 the trabeculae ; a quantity of starch accumulates in these parts. The 

 external part and some detached portions in the interior are all that 

 is left of the formative tissue, or else it is only the lower part of the 

 sporange which degenerates into amyliferous tissue, the upper part, 

 which is constricted off from it, forming the spores, which may some- 

 times ripen. Thirdly (3), the sporange is sometimes observed to be 

 converted, after its formation, into amyliferous tissue. It then preserves 

 its shape, but remains very small ; or it may develop small protu- 

 berances on its surface. These may advance to the condition of leaves, 



* See this Journal, ante, p. 96. t Comptes Eeridus, xcii. (1881) pp. 310-12. 



