TRANSACTIONS OF SECTION C. 753 



The capsules are more or less spherical, and measure 0'7o mm. iu diameter. 

 Those which are broken are seen to contain a granular mass of spores. The more 

 perfect capsules have a wall which appears tessellated, as it is composed of small 

 quadrate cells. 



Sections of the capsules show that the spores are still connected into tetrads 

 by the spore mother cell-walls. The coats of the spores are covered with minute 

 bosses. The sporangium wall is at least one cell layer thick. 



Sections of the vegetative parts do not reveal any details of structure, but some 

 points may be made out by simply rubbing down on a hone. Long tubes filled 

 up with oxide of iron lying in the axes of the stems are all that is preserved of the 

 internal tissues. The tubes may occasionally be found sending a branch to a leaf. 



The nature and position of the sporangia and their contents suggest that 

 Naiadita had affinities with Lycopods rather than with mosses. 



On this account I searched thoroughly for stomata, as structures confirmatory 

 of the sporophytic nature of the plant. The result of the search was, as I have 

 said, negative, and it is not surprising that this should be the case. The associated 

 fossils are freshwater forms, and the habits of the plant point to a submerged 

 existence. Mr. Gardner has already appreciated this fact in maintaining the close 

 kinship of Naiadita with Fontinalis. The submerged species of Isoetes show that 

 aquatic life in the case of Cryptogams leads to loss of stomata just as in that of 

 Phanerogams, 



2 The Influence of the Winds upon Climate during Past Epochs : a 

 Meteorological Explanation of some Geological Problems. By F. W. 

 Harmer, F.G.S. 



This paper is in continuation of one read at Dover in 1899, on ' The Meteoro- 

 logical Conditions of North-western Europe during the Pliocene and Glacial 

 Periods.' 



The irregular distrihution of the isotherms in the northern hemisphere is 

 largely due to the direction of the prevalent winds. In regions where these are 

 constantly varying, as, for example, in Great Britain, the climate varies diurnally, 

 one day being often dry or cold, and the next rainy or warm. In others, where 

 the wind changes seasonally, one part of the year is rainless and another pluvial. 

 Permanent alterations in climate would equally result were the course of the pre- 

 valent winds permanently changed. 



The direction of the winds, which must always be more or less parallel to the 

 isobars, depends on the relative position, and on the form and alignment of areas 

 of high and low barometric pressure. The movements of the latter being largely 

 interdependent, any important meteorological disturbance, however caused, may 

 make its influence felt at a considerable distance from the focus of its origin. 



The winds blow round areas of high and low pressure ; outwards, from the 

 former, and to the north of the Equator, from left to right : and inwards, towards 

 tlio latter, from right to left. Hence, in the northern hemisphere, southerly 

 winds prevail to the east of a cyclonic centre, and northerly winds to the west of 

 it, the contrast between the temperature of the two being usually in proportion 

 to the distance the aerial currents may have travelled from the south and the 

 north respectively. Warm and cold winds must therefore necessarily coexist, 

 causing differences in climate in countries having the same latitude. The winter 

 temperature of Hudson's Bay is, for example, 60^ F. colder than that of Great 

 Britain. Similar climatal conditions must also have existed during the Pleistocene 

 epoch. 



The continental regions of the northern hemisphere, being at present warmer 

 during summer than the ocean, are cyclonic ; in winter they are colder, and con- 

 sequently anticyclonic. Over the great ice-sheets of the Glacial period, however, 

 high pressure must have prevailed, more or less, at all season.^, and, generally, the 

 meteorological conditions, including the direction of the prevalent winds, and local 

 variations iu climatt must then have been widely different from those of our own 



1900 3 c 



