128 



HAEDWICKE'S SCIENCE-GOSSIP. 



[Jttne 1, 186S. 



two parts. The " veinage," lie says, "consisted of 

 two laminae;" and asks "whether botanists have 

 observed a similar state of things with other leaves." 

 Here, agaiu, a little more anatomical knowledge 

 would have informed him that not to be able to 

 separate the bundle of woody tissue, of which the 

 vein is composed, into an vpper and lower layer 

 would prove the exception rather than the rule. 

 Tor in the anatomical structure of the leaf, the fibro- 

 vascular tissue (vein) proceeding from the medullary 

 sheath, after having passed from the origin of the 

 leaf to its extremity, doubles back upon itself, form- 

 ing underneath the first a new layer of fibre, which 

 finally discharges itself into the liber. So that the 

 bundle of woody fibre which forms the framework 

 or skeleton of the leaf communicates above with the 

 medullary sheath, and below with the liber. The 

 double layer of fibro-vascular tissue is also per- 

 ceptible in a leaf which has laiu during the winter 

 in some damp ditch. When its cellular substance is 

 decayed, so that the cohesion between the upper 

 and lower layers is destroyed, they can then be easily 

 separated. The curious Indian leaves which have 

 the property for opening on slight violence like the 

 leg of a silk stocking, so that the hand may be thrust 

 between their upper and lower surfaces, derive that 

 singular separability from an imperfect union be- 

 tween the excurrent and recurrent fibre. 



The strong impression entertained by "T. W.W." 

 that the marginal vein will be found in many de- 

 ciduous plants, will, I conceive, be materially 

 strengthened when he has found this to be the 

 case ; until then, his negativing the idea that it is 

 peculiar to the Umbelliferse remains harmless, and 

 simply stands for what is worth — an impression. 



Before concluding, I may be allowed to remark 

 that it is likely a considerable number of leaves will 

 be found amongst different orders of plants in which 

 a vein at the very edge will manifest itself. I have 

 before me descriptions of more than one hundred 

 leaves, not of the umbelliferous group, in some of 

 which the vein in question is distinct and unmis- 

 takable. Not even two, hoicever, in one order yet. 

 It is the finding it in large numbers in one order 

 that gives character to that order. 



I notice it in the Box, of which some descriptions 

 of leaves no less than one inch and three-tenths in 

 length are in my possession ; in the Holly and the 

 Barberry ; and it is beautifully displayed in the ex- 

 panded shoots — formerly considered leaves — of the 

 Butcher's Broom (Ruscus aculeatus). 



It is to be hoped, therefore, that the insignifi- 

 cant number furnished by " T. W. W.," and already 

 known to myself, may increase, so that the mar- 

 ginal vein may ere long become dignified by having 

 a class of its own. 



The plan of boiling leaves in liquor potassse is 

 one which is well adapted for procuring their skele- 

 tons easily and expeditiously. It will be found in 



practice, however, that there are scarcely two 

 different leaves that bear the same amount of boil- 

 ing. What would just suffice for the Box, for in- 

 stance, would disintegrate the Myrtle into shreds, 

 and what would spoil the Myrtle would scarcely 

 affect the Barberry. But as it is only by experiment 

 that the proper time for keeping a leaf in the 

 boiling fluid can be ascertained, it is but to leave 

 this to those who may wish to prosecute the inquiry 

 for themselves. 



Finally, the skeletons of those leaves which are 

 so thick and opaque that the microscope fails to 

 develop their modes of venation, are those which 

 more particularly demand dissection for the pur- 

 poses of description and classification. The more 

 transparent leaves may be entrusted to the micro- 

 scope. John Gorham. 



Tanbriclge. 



THE ALIMENTARY SYSTEM OE 

 A HOUSE SPIDER. 



TEGENARIA CIVILIS, the anatomy of whose 

 alimentary system I am about to describe, 

 belongs, as do most of the animals popularly 

 termed " spiders," to the family Araneidse of the 

 Arachnida pulmonaria or filosa. 



Although all my observations will refer more par- 

 ticularly to the species I have chosen for illustra- 

 tion, many of them might with propriety be applied 

 to any other member of the Araneidse. But in 

 such a large family as this there are in every 

 genus minute differences of structure, the descrip- 

 tion of all of which would far exceed the limits 

 of a short article. 1 therefore thought it better 

 to confine myself to one in particular, in place of 

 trying to take a cursory view of the whole. 



I have chosen the Tegenaria civilis as the basis of 

 my remarks for several reasons, but chiefly because it 

 is a very common, if not the most common, of our 

 British spiders; and there must be few of my readers 

 who have not seen it lurking in its web when they 

 were moving some old article of furniture, or visit- 

 ing some remote garret or lumber-room, and thus 

 have acquired a knowledge of its general appear- 

 ance at least. 



The term alimentary system I have employed in its 

 widest sense, including in it all organs directly or 

 indirectly subservient to the nourishment ' of the 

 animal — such, for instance, as the spinnerets, from 

 which are eliminated those wonderful webs in which 

 the spider snares its prey. 



With these few words of preface, I will now pro- 

 ceed with the immediate subject of my paper, 

 and commence by describing what are called the 

 " falces." 



The falces are a pair of jaw-like organs situ- 

 ated immediately above the mouth ; they are at- 



